Hello!
where are problems with send and recieving sms on this modem.
trying smsd v.3.1.15 and v.3.1.16.
i try to read sms from AT+CMGR=0 and modem answers with OK and then sends sms stored in 0 memory.
but for AT+CMGR=20 we always get +CMS ERROR: 500
and i don't undersand why then smsd send sms modem answers with +CMS ERROR: 500
trying send with "hands" sms sended without problems

log from 3.1.15
....
2016-12-29 20:31:03,6, GSM1: Trying to get stored message 20
2016-12-29 20:31:04,7, GSM1: -> AT+CMGR=20
2016-12-29 20:31:04,7, GSM1: Command is sent, waiting for the answer
2016-12-29 20:31:04,7, GSM1: <- +CMS ERROR: 500 (Unknown error)
2016-12-29 20:31:04,6, GSM1: Checking device for incoming SMS
2016-12-29 20:31:04,6, GSM1: Checking memory size
2016-12-29 20:31:04,7, GSM1: -> AT+CPMS?
2016-12-29 20:31:04,7, GSM1: Command is sent, waiting for the answer
2016-12-29 20:31:04,7, GSM1: <- +CPMS: "ME",1,20,"ME",1,20,"ME",1,20 OK
....
and log from 3.1.16
....
2016-12-30 11:44:31,5, GSM1: Waiting 10 sec. before retrying
2016-12-30 11:44:41,6, GSM1: Checking if modem is ready
2016-12-30 11:44:41,7, GSM1: -> AT
2016-12-30 11:44:41,7, GSM1: Command is sent, waiting for the answer. (5)
2016-12-30 11:44:41,7, GSM1: <- OK
2016-12-30 11:44:41,6, GSM1: Pre-initializing modem
2016-12-30 11:44:41,7, GSM1: -> ATE0+CMEE=1;+CREG=2
2016-12-30 11:44:41,7, GSM1: Command is sent, waiting for the answer. (10)
2016-12-30 11:44:41,7, GSM1: <- OK
2016-12-30 11:44:41,6, GSM1: Checking if modem needs PIN
2016-12-30 11:44:41,7, GSM1: -> AT+CPIN?
2016-12-30 11:44:41,7, GSM1: Command is sent, waiting for the answer. (10)
2016-12-30 11:44:42,7, GSM1: <- +CPIN: READY OK
2016-12-30 11:44:42,6, GSM1: Initializing modem
2016-12-30 11:44:42,7, GSM1: -> AT+CPMS="ME","ME","ME"
2016-12-30 11:44:42,7, GSM1: Command is sent, waiting for the answer. (10)
2016-12-30 11:44:42,7, GSM1: <- +CPMS: 0,20,0,20,0,20 OK
2016-12-30 11:44:42,7, GSM1: -> AT+CSQ
2016-12-30 11:44:42,7, GSM1: Command is sent, waiting for the answer. (10)
2016-12-30 11:44:42,7, GSM1: <- +CSQ: 7,99 OK
2016-12-30 11:44:42,6, GSM1: Signal Strength Indicator: (7,99) -99 dBm (Marginal), Bit Error Rate: not known or not detectable
2016-12-30 11:44:42,6, GSM1: Checking if Modem is registered to the network
2016-12-30 11:44:43,7, GSM1: -> AT+CREG?
2016-12-30 11:44:43,7, GSM1: Command is sent, waiting for the answer. (10)
2016-12-30 11:44:43,7, GSM1: <- +CREG: 2,1,"B79B","9EAD" OK
2016-12-30 11:44:43,6, GSM1: Modem is registered to the network
2016-12-30 11:44:43,6, GSM1: Selecting PDU mode
2016-12-30 11:44:43,7, GSM1: -> AT+CMGF=0
2016-12-30 11:44:43,7, GSM1: Command is sent, waiting for the answer. (5)
2016-12-30 11:44:43,7, GSM1: <- OK
2016-12-30 11:44:43,7, GSM1: -> AT+CMGS=21
2016-12-30 11:44:43,7, GSM1: Command is sent, waiting for the answer. (10)
2016-12-30 11:44:43,7, GSM1: <- >
2016-12-30 11:44:43,7, GSM1: -> XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
2016-12-30 11:44:43,7, GSM1: Command is sent, waiting for the answer. (60)
2016-12-30 11:45:12,7, GSM1: <- +CMS ERROR: 500 (Unknown error)
2016-12-30 11:45:12,3, GSM1: The modem answer was not OK: +CMS ERROR: 500 (Unknown error)
2016-12-30 11:45:12,4, GSM1: Sending SMS to XXXXXXXXXX failed, trying time 116 sec. Retries: 2.
.....

and this what we have for now.
awaiting for patch resolving this problem
log from 3.1.15
....
2016-12-30 14:00:55,7, GSM1: -> AT+CMGF=0
2016-12-30 14:00:55,7, GSM1: Command is sent, waiting for the answer
2016-12-30 14:00:56,7, GSM1: <- OK
2016-12-30 14:00:56,7, GSM1: -> AT+CMGS=134
2016-12-30 14:00:56,7, GSM1: Command is sent, waiting for the answer
2016-12-30 14:00:56,7, GSM1: <- >
2016-12-30 14:00:56,7, GSM1: -> xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
2016-12-30 14:00:56,7, GSM1: Command is sent, waiting for the answer
................
2016-12-30 14:01:28,7, GSM1: <- ^RSSI: 8 +CMS ERROR: 500 (Unknown error)
2016-12-30 14:01:28,3, GSM1: The modem answer was not OK: ^RSSI: 8+CMS ERROR: 500 (Unknown error)
2016-12-30 14:01:28,5, GSM1: Waiting 10 sec. before retrying
2016-12-30 14:01:38,6, GSM1: Checking if modem is ready
2016-12-30 14:01:39,3, GSM1: Unexpected input: ^RSSI: 8
2016-12-30 14:01:39,7, GSM1: -> AT
2016-12-30 14:01:39,7, GSM1: Command is sent, waiting for the answer
2016-12-30 14:01:39,7, GSM1: <- OK
2016-12-30 14:01:39,6, GSM1: Pre-initializing modem
2016-12-30 14:01:39,7, GSM1: -> ATE0+CMEE=1;+CREG=2
2016-12-30 14:01:39,7, GSM1: Command is sent, waiting for the answer
2016-12-30 14:01:39,7, GSM1: <- OK
2016-12-30 14:01:39,6, GSM1: Checking if modem needs PIN
2016-12-30 14:01:40,7, GSM1: -> AT+CPIN?
2016-12-30 14:01:40,7, GSM1: Command is sent, waiting for the answer
2016-12-30 14:01:40,7, GSM1: <- +CPIN: READY OK
2016-12-30 14:01:40,6, GSM1: Initializing modem
2016-12-30 14:01:40,7, GSM1: -> AT+CPMS="ME","ME","ME"
2016-12-30 14:01:40,7, GSM1: Command is sent, waiting for the answer
2016-12-30 14:01:41,7, GSM1: <- +CPMS: 0,20,0,20,0,20 OK
2016-12-30 14:01:41,7, GSM1: -> AT+CSQ
2016-12-30 14:01:41,7, GSM1: Command is sent, waiting for the answer
2016-12-30 14:01:41,7, GSM1: <- +CSQ: 8,99 OK
2016-12-30 14:01:41,6, GSM1: Signal Strength Indicator: (8,99) -97 dBm (Marginal), Bit Error Rate: not known or not detectable
2016-12-30 14:01:41,6, GSM1: Checking if Modem is registered to the network
2016-12-30 14:01:41,7, GSM1: -> AT+CREG?
2016-12-30 14:01:41,7, GSM1: Command is sent, waiting for the answer
2016-12-30 14:01:42,7, GSM1: <- +CREG: 2,1,"B79B","9EAD" OK
2016-12-30 14:01:42,6, GSM1: Modem is registered to the network
2016-12-30 14:01:42,6, GSM1: Selecting PDU mode
2016-12-30 14:01:42,7, GSM1: -> AT+CMGF=0
2016-12-30 14:01:42,7, GSM1: Command is sent, waiting for the answer
2016-12-30 14:01:42,7, GSM1: <- OK
2016-12-30 14:01:42,7, GSM1: -> AT+CMGS=134
2016-12-30 14:01:42,7, GSM1: Command is sent, waiting for the answer
2016-12-30 14:01:43,7, GSM1: <- >
2016-12-30 14:01:43,7, GSM1: -> xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
2016-12-30 14:01:43,7, GSM1: Command is sent, waiting for the answer
2016-12-30 14:02:12,7, GSM1: <- ^RSSI: 7 ^RSSI: 11 +CMS ERROR: 500 (Unknown error)
2016-12-30 14:02:12,3, GSM1: The modem answer was not OK: ^RSSI: 7^RSSI: 11+CMS ERROR: 500 (Unknown error)
2016-12-30 14:02:12,5, GSM1: Waiting 10 sec. before retrying
2016-12-30 14:02:22,6, GSM1: Checking if modem is ready
2016-12-30 14:02:23,3, GSM1: Unexpected input: ^RSSI: 11 ^RSSI: 8
2016-12-30 14:02:23,7, GSM1: -> AT
2016-12-30 14:02:23,7, GSM1: Command is sent, waiting for the answer
2016-12-30 14:02:23,7, GSM1: <- OK
2016-12-30 14:02:23,6, GSM1: Pre-initializing modem
2016-12-30 14:02:23,7, GSM1: -> ATE0+CMEE=1;+CREG=2
2016-12-30 14:02:23,7, GSM1: Command is sent, waiting for the answer
2016-12-30 14:02:23,7, GSM1: <- OK
2016-12-30 14:02:23,6, GSM1: Checking if modem needs PIN
2016-12-30 14:02:24,7, GSM1: -> AT+CPIN?
2016-12-30 14:02:24,7, GSM1: Command is sent, waiting for the answer
2016-12-30 14:02:24,7, GSM1: <- +CPIN: READY OK
2016-12-30 14:02:24,6, GSM1: Initializing modem
2016-12-30 14:02:24,7, GSM1: -> AT+CPMS="ME","ME","ME"
2016-12-30 14:02:24,7, GSM1: Command is sent, waiting for the answer
2016-12-30 14:02:25,7, GSM1: <- +CPMS: 0,20,0,20,0,20 OK
2016-12-30 14:02:25,7, GSM1: -> AT+CSQ
2016-12-30 14:02:25,7, GSM1: Command is sent, waiting for the answer
2016-12-30 14:02:25,7, GSM1: <- +CSQ: 8,99 OK
2016-12-30 14:02:25,6, GSM1: Signal Strength Indicator: (8,99) -97 dBm (Marginal), Bit Error Rate: not known or not detectable
2016-12-30 14:02:25,6, GSM1: Checking if Modem is registered to the network
2016-12-30 14:02:25,7, GSM1: -> AT+CREG?
2016-12-30 14:02:25,7, GSM1: Command is sent, waiting for the answer
2016-12-30 14:02:26,7, GSM1: <- +CREG: 2,1,"B79B","9EAD" OK
2016-12-30 14:02:26,6, GSM1: Modem is registered to the network
2016-12-30 14:02:26,6, GSM1: Selecting PDU mode
2016-12-30 14:02:26,7, GSM1: -> AT+CMGF=0
2016-12-30 14:02:26,7, GSM1: Command is sent, waiting for the answer
2016-12-30 14:02:26,7, GSM1: <- OK
2016-12-30 14:02:26,7, GSM1: -> AT+CMGS=134
2016-12-30 14:02:26,7, GSM1: Command is sent, waiting for the answer
2016-12-30 14:02:27,7, GSM1: <- >

But now then we get unexpected answer after CMGS - everything is ok

2016-12-30 14:02:27,3, GSM1: Unexpected input: ^RSSI: 4
2016-12-30 14:02:27,7, GSM1: -> XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
2016-12-30 14:02:27,7, GSM1: Command is sent, waiting for the answer
2016-12-30 14:02:29,7, GSM1: <- +CMGS: 125 OK

2016-12-30 14:02:29,5, GSM1: SMS sent, Message_id: 125, To: XXXXXXXXXXXX, sending time 97 sec. Retries: 2.
2016-12-30 14:02:29,6, GSM1: Moved file /var/spool/sms/checked/send_p7iDE1 to /var/spool/sms/sent/send_p7iDE1
2016-12-30 14:02:29,6, GSM1: I have to send 1 short message for /var/spool/sms/checked/send_9BXKW3
....

For reading messages you have to use a modem setting:
memory_start = 0

To get rid of unexpected input use a modem setting:
init2 = AT^CURC=0

If this does not completely help, try a setting:
init2 = AT^CURC=0;^BOOT=0,0;^U2DIAG=0

If the sending still fails, I need to see the PDU. You can use Private tag to protect it, so it's visible only for me and you. Also show the PDU wich was sent properly.

keke wrote

For reading messages you have to use a modem setting:
memory_start = 0
already

If this does not completely help, try a setting:
init2 = AT^CURC=0;^BOOT=0,0;^U2DIAG=0
u2diag=0 for this modem don't work and modem detected without problems

with init2 = AT^CURC=0;^BOOT=0,0, log is:

2016-12-31 11:32:47,7, GSM1: -> ATE0+CMEE=1;+CREG=2
2016-12-31 11:32:47,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:32:47,7, GSM1: <- OK
2016-12-31 11:32:47,6, GSM1: Checking if modem needs PIN
2016-12-31 11:32:48,7, GSM1: -> AT+CPIN?
2016-12-31 11:32:48,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:32:48,7, GSM1: <- +CPIN: READY OK
2016-12-31 11:32:48,6, GSM1: Initializing modem
2016-12-31 11:32:48,7, GSM1: -> AT+CPMS="ME","ME","ME"
2016-12-31 11:32:48,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:32:49,7, GSM1: <- +CPMS: 0,20,0,20,0,20 OK
2016-12-31 11:32:49,7, GSM1: -> AT^CURC=0;^BOOT=0,0
2016-12-31 11:32:49,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:32:49,7, GSM1: <- OK
2016-12-31 11:32:49,7, GSM1: -> AT+CSQ
2016-12-31 11:32:49,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:32:50,7, GSM1: <- +CSQ: 6,99 OK
2016-12-31 11:32:50,6, GSM1: Signal Strength Indicator: (6,99) -101 dBm (Marginal), Bit Error Rate: not known or not detectable
2016-12-31 11:32:50,6, GSM1: Checking if Modem is registered to the network
2016-12-31 11:32:50,7, GSM1: -> AT+CREG?
2016-12-31 11:32:50,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:32:50,7, GSM1: <- +CREG: 2,1,"B79B","9EAD" OK
2016-12-31 11:32:50,6, GSM1: Modem is registered to the network
2016-12-31 11:32:50,6, GSM1: Selecting PDU mode
2016-12-31 11:32:50,7, GSM1: -> AT+CMGF=0
2016-12-31 11:32:50,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:32:51,7, GSM1: <- OK
2016-12-31 11:32:51,7, GSM1: -> AT+CMGS=137
2016-12-31 11:32:51,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:32:51,7, GSM1: <- >
2016-12-31 11:32:51,7, GSM1: ->

Hidden private text.

.
2016-12-31 11:32:51,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:32:56,5, smsd: Moved file /var/spool/sms/outgoing/send_P41eZn to /var/spool/sms/checked
2016-12-31 11:32:57,5, smsd: Moved file /var/spool/sms/outgoing/send_mlIhfd to /var/spool/sms/checked
2016-12-31 11:32:57,5, smsd: Moved file /var/spool/sms/outgoing/send_d0400w to /var/spool/sms/checked
2016-12-31 11:32:58,5, smsd: Moved file /var/spool/sms/outgoing/send_TNc6iG to /var/spool/sms/checked
2016-12-31 11:32:59,5, smsd: Moved file /var/spool/sms/outgoing/send_TB521H to /var/spool/sms/checked
2016-12-31 11:32:59,5, smsd: Moved file /var/spool/sms/outgoing/send_G59kUd to /var/spool/sms/checked
2016-12-31 11:33:00,5, smsd: Moved file /var/spool/sms/outgoing/send_Equvjl to /var/spool/sms/checked
2016-12-31 11:33:10,5, smsd: Moved file /var/spool/sms/outgoing/send_tdhD7K to /var/spool/sms/checked
2016-12-31 11:33:22,7, GSM1: <- +CMS ERROR: 500 (Unknown error)
2016-12-31 11:33:22,3, GSM1: The modem answer was not OK: +CMS ERROR: 500 (Unknown error)
2016-12-31 11:33:22,5, GSM1: Waiting 10 sec. before retrying
2016-12-31 11:33:32,6, GSM1: Checking if modem is ready
2016-12-31 11:33:32,7, GSM1: -> AT
2016-12-31 11:33:32,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:33:32,7, GSM1: <- OK
2016-12-31 11:33:32,6, GSM1: Pre-initializing modem
2016-12-31 11:33:32,7, GSM1: -> ATE0+CMEE=1;+CREG=2
2016-12-31 11:33:32,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:33:33,7, GSM1: <- OK
2016-12-31 11:33:33,6, GSM1: Checking if modem needs PIN
2016-12-31 11:33:33,7, GSM1: -> AT+CPIN?
2016-12-31 11:33:33,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:33:33,7, GSM1: <- +CPIN: READY OK
2016-12-31 11:33:33,6, GSM1: Initializing modem
2016-12-31 11:33:33,7, GSM1: -> AT+CPMS="ME","ME","ME"
2016-12-31 11:33:33,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:33:34,7, GSM1: <- +CPMS: 0,20,0,20,0,20 OK
2016-12-31 11:33:34,7, GSM1: -> AT^CURC=0;^BOOT=0,0
2016-12-31 11:33:34,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:33:34,7, GSM1: <- OK
2016-12-31 11:33:35,7, GSM1: -> AT+CSQ
2016-12-31 11:33:35,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:33:35,7, GSM1: <- +CSQ: 7,99 OK
2016-12-31 11:33:35,6, GSM1: Signal Strength Indicator: (7,99) -99 dBm (Marginal), Bit Error Rate: not known or not detectable
2016-12-31 11:33:35,6, GSM1: Checking if Modem is registered to the network
2016-12-31 11:33:35,7, GSM1: -> AT+CREG?
2016-12-31 11:33:35,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:33:35,7, GSM1: <- +CREG: 2,1,"B79B","9EAD" OK
2016-12-31 11:33:35,6, GSM1: Modem is registered to the network
2016-12-31 11:33:35,6, GSM1: Selecting PDU mode
2016-12-31 11:33:36,7, GSM1: -> AT+CMGF=0
2016-12-31 11:33:36,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:33:36,7, GSM1: <- OK
2016-12-31 11:33:36,7, GSM1: -> AT+CMGS=137
2016-12-31 11:33:36,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:33:36,7, GSM1: <- >
2016-12-31 11:33:37,7, GSM1: ->

Hidden private text.

.
2016-12-31 11:33:37,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:34:05,7, GSM1: <- +CMS ERROR: 500 (Unknown error)
2016-12-31 11:34:05,3, GSM1: The modem answer was not OK: +CMS ERROR: 500 (Unknown error)
2016-12-31 11:34:05,5, GSM1: Waiting 10 sec. before retrying
2016-12-31 11:34:15,6, GSM1: Checking if modem is ready
2016-12-31 11:34:15,7, GSM1: -> AT
2016-12-31 11:34:15,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:34:15,7, GSM1: <- OK
2016-12-31 11:34:15,6, GSM1: Pre-initializing modem
2016-12-31 11:34:16,7, GSM1: -> ATE0+CMEE=1;+CREG=2
2016-12-31 11:34:16,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:34:16,7, GSM1: <- OK
2016-12-31 11:34:16,6, GSM1: Checking if modem needs PIN
2016-12-31 11:34:16,7, GSM1: -> AT+CPIN?
2016-12-31 11:34:16,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:34:16,7, GSM1: <- +CPIN: READY OK
2016-12-31 11:34:16,6, GSM1: Initializing modem
2016-12-31 11:34:17,7, GSM1: -> AT+CPMS="ME","ME","ME"
2016-12-31 11:34:17,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:34:17,7, GSM1: <- +CPMS: 0,20,0,20,0,20 OK
2016-12-31 11:34:17,7, GSM1: -> AT^CURC=0;^BOOT=0,0
2016-12-31 11:34:17,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:34:18,7, GSM1: <- OK
2016-12-31 11:34:18,7, GSM1: -> AT+CSQ
2016-12-31 11:34:18,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:34:18,7, GSM1: <- +CSQ: 5,99 OK
2016-12-31 11:34:18,6, GSM1: Signal Strength Indicator: (5,99) -103 dBm (Marginal), Bit Error Rate: not known or not detectable
2016-12-31 11:34:18,6, GSM1: Checking if Modem is registered to the network
2016-12-31 11:34:18,7, GSM1: -> AT+CREG?
2016-12-31 11:34:18,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:34:19,7, GSM1: <- +CREG: 2,1,"B79B","9EAD" OK
2016-12-31 11:34:19,6, GSM1: Modem is registered to the network
2016-12-31 11:34:19,6, GSM1: Selecting PDU mode
2016-12-31 11:34:19,7, GSM1: -> AT+CMGF=0
2016-12-31 11:34:19,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:34:19,7, GSM1: <- OK
2016-12-31 11:34:19,7, GSM1: -> AT+CMGS=137
2016-12-31 11:34:19,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:34:20,7, GSM1: <- >
2016-12-31 11:34:20,7, GSM1: ->

Hidden private text.

.
2016-12-31 11:34:20,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:34:48,7, GSM1: <- +CMS ERROR: 500 (Unknown error)
2016-12-31 11:34:48,3, GSM1: The modem answer was not OK: +CMS ERROR: 500 (Unknown error)
2016-12-31 11:34:48,4, GSM1: Sending SMS to

Hidden private text.

failed, trying time 122 sec. Retries: 2.

but if i remove from conf file init2 = AT^CURC=0;^BOOT=0,0, and after restart smsd
......................
2016-12-31 11:49:23,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:49:23,7, GSM1: <- +CPMS: 0,20,0,20,0,20 OK
2016-12-31 11:49:24,7, GSM1: -> AT+CSQ
2016-12-31 11:49:24,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:49:24,7, GSM1: <- +CSQ: 6,99 OK
2016-12-31 11:49:24,6, GSM1: Signal Strength Indicator: (6,99) -101 dBm (Marginal), Bit Error Rate: not known or not detectable
2016-12-31 11:49:24,6, GSM1: Checking if Modem is registered to the network
2016-12-31 11:49:24,7, GSM1: -> AT+CREG?
2016-12-31 11:49:24,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:49:24,7, GSM1: <- +CREG: 2,1,"B79B","9EAD" OK
2016-12-31 11:49:24,6, GSM1: Modem is registered to the network
2016-12-31 11:49:24,6, GSM1: Selecting PDU mode
2016-12-31 11:49:25,7, GSM1: -> AT+CMGF=0
2016-12-31 11:49:25,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:49:25,7, GSM1: <- OK
2016-12-31 11:49:25,7, GSM1: -> AT+CMGS=134
2016-12-31 11:49:25,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:49:25,7, GSM1: <- >
2016-12-31 11:49:26,7, GSM1: ->

Hidden private text.

2016-12-31 11:49:26,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:49:54,7, GSM1: <- +CMS ERROR: 500 (Unknown error)
2016-12-31 11:49:54,3, GSM1: The modem answer was not OK: +CMS ERROR: 500 (Unknown error)
2016-12-31 11:49:54,4, GSM1: Sending SMS to 998985752022 failed, trying time 118 sec. Retries: 2.
2016-12-31 11:49:54,6, GSM1: Moved file /var/spool/sms/checked/send_HW95Lr to /var/spool/sms/failed/send_HW95Lr
2016-12-31 11:49:54,2, GSM1: Fatal error: sending failed 3 times. Blocking 3600 sec.
2016-12-31 11:54:22,2, smsd: Smsd mainprocess is awaiting the termination of all modem handlers. PID: 2523.
2016-12-31 11:54:22,2, GSM1: Modem handler 0 terminated. PID: 2524, was started 16-12-31 11:42:36.
2016-12-31 11:54:22,2, smsd: Smsd mainprocess terminated. PID 2523, was started 16-12-31 11:42:36.
2016-12-31 11:54:23,2, smsd: Smsd v3.1.15 started.
2016-12-31 11:54:23,2, smsd: Running as root:root.
2016-12-31 11:54:23,7, smsd: Running startup_check (shell): /var/spool/sms/incoming/smsd_script.YWYRmk /tmp/smsd_data.nrDMnP
2016-12-31 11:54:23,7, smsd: Done: startup_check (shell), execution time 0 sec., status: 0 (0)
2016-12-31 11:54:23,4, smsd: File mode creation mask: 022 (0644, rw-r--r--).
2016-12-31 11:54:23,5, smsd: Outgoing file checker has started. PID: 2557.
2016-12-31 11:54:23,7, smsd: All PID's: 2557,2559
2016-12-31 11:54:23,5, GSM1: Modem handler 0 has started. PID: 2559.
2016-12-31 11:54:23,5, GSM1: Using check_memory_method 1: CPMS is used.
2016-12-31 11:54:23,6, GSM1: I have to send 1 short message for /var/spool/sms/checked/send_P41eZn
2016-12-31 11:54:23,6, GSM1: Sending SMS from to

Hidden private text.

2016-12-31 11:54:23,6, GSM1: Checking if modem is ready
2016-12-31 11:54:24,7, GSM1: -> AT
2016-12-31 11:54:24,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:54:24,7, GSM1: <- OK
2016-12-31 11:54:24,6, GSM1: Pre-initializing modem
2016-12-31 11:54:24,7, GSM1: -> ATE0+CMEE=1;+CREG=2
2016-12-31 11:54:24,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:54:24,7, GSM1: <- OK
2016-12-31 11:54:24,6, GSM1: Checking if modem needs PIN
2016-12-31 11:54:25,7, GSM1: -> AT+CPIN?
2016-12-31 11:54:25,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:54:25,7, GSM1: <- +CPIN: READY OK
2016-12-31 11:54:25,6, GSM1: Initializing modem
2016-12-31 11:54:25,7, GSM1: -> AT+CPMS="ME","ME","ME"
2016-12-31 11:54:25,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:54:26,7, GSM1: <- +CPMS: 0,20,0,20,0,20 OK
2016-12-31 11:54:26,7, GSM1: -> AT+CSQ
2016-12-31 11:54:26,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:54:26,7, GSM1: <- +CSQ: 14,99 OK
2016-12-31 11:54:26,6, GSM1: Signal Strength Indicator: (14,99) -85 dBm (Workable), Bit Error Rate: not known or not detectable
2016-12-31 11:54:26,6, GSM1: Checking if Modem is registered to the network
2016-12-31 11:54:26,7, GSM1: -> AT+CREG?
2016-12-31 11:54:26,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:54:27,7, GSM1: <- +CREG: 2,1,"0BBE","2EF5" OK
2016-12-31 11:54:27,6, GSM1: Modem is registered to the network
2016-12-31 11:54:27,6, GSM1: Location area code: 0BBE, Cell ID: 2EF5
2016-12-31 11:54:27,7, GSM1: -> AT+CSQ
2016-12-31 11:54:27,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:54:27,7, GSM1: <- +CSQ: 14,99 OK
2016-12-31 11:54:27,6, GSM1: Signal Strength Indicator: (14,99) -85 dBm (Workable), Bit Error Rate: not known or not detectable
2016-12-31 11:54:27,6, GSM1: Selecting PDU mode
2016-12-31 11:54:27,7, GSM1: -> AT+CMGF=0
2016-12-31 11:54:27,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:54:28,7, GSM1: <- OK
2016-12-31 11:54:28,7, GSM1: -> AT+CIMI
2016-12-31 11:54:28,7, GSM1: Command is sent, waiting for the answer

Hidden private text.

2016-12-31 11:54:28,7, GSM1: -> AT+CGSN
2016-12-31 11:54:28,7, GSM1: Command is sent, waiting for the answer

Hidden private text.

2016-12-31 11:54:29,6, GSM1: Checking if reading of messages is supported
2016-12-31 11:54:29,7, GSM1: -> AT+CPMS?
2016-12-31 11:54:29,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:54:29,7, GSM1: <- +CPMS: "ME",0,20,"ME",0,20,"ME",0,20 OK
2016-12-31 11:54:29,7, GSM1: -> AT+CMGS=134
2016-12-31 11:54:29,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:54:30,7, GSM1: <- >
2016-12-31 11:54:30,7, GSM1: ->

Hidden private text.

F.
2016-12-31 11:54:30,7, GSM1: Command is sent, waiting for the answer
2016-12-31 11:54:34,7, GSM1: <- +CMGS: 158 OK
2016-12-31 11:54:34,5, GSM1: SMS sent, Message_id: 158, To:

Hidden private text.

, sending time 11 sec.
2016-12-31 11:54:34,6, GSM1: Moved file /var/spool/sms/checked/send_P41eZn to /var/spool/sms/sent/send_P41eZn
2016-12-31 11:54:34,6, GSM1: I have to send 1 short message for /var/spool/sms/checked/send_d0400w
2016-12-31 11:54:34,6, GSM1: Sending SMS from to

Hidden private text.

.............
but after some time we have:
..............
2016-12-31 12:00:38,6, GSM1: Checking if Modem is registered to the network
2016-12-31 12:00:38,7, GSM1: -> AT+CREG?
2016-12-31 12:00:38,7, GSM1: Command is sent, waiting for the answer
2016-12-31 12:00:38,7, GSM1: <- +CREG: 2,1,"B79B","9EAD" OK
2016-12-31 12:00:38,6, GSM1: Modem is registered to the network
2016-12-31 12:00:38,6, GSM1: Selecting PDU mode
2016-12-31 12:00:38,7, GSM1: -> AT+CMGF=0
2016-12-31 12:00:38,7, GSM1: Command is sent, waiting for the answer
2016-12-31 12:00:39,7, GSM1: <- OK
2016-12-31 12:00:39,7, GSM1: -> AT+CMGS=28
2016-12-31 12:00:39,7, GSM1: Command is sent, waiting for the answer
2016-12-31 12:00:39,7, GSM1: <- >
2016-12-31 12:00:39,7, GSM1: ->

Hidden private text.

2016-12-31 12:00:39,7, GSM1: Command is sent, waiting for the answer
2016-12-31 12:01:08,7, GSM1: <- +CMS ERROR: 500 (Unknown error)
2016-12-31 12:01:08,3, GSM1: The modem answer was not OK: +CMS ERROR: 500 (Unknown error)
2016-12-31 12:01:08,5, GSM1: Waiting 10 sec. before retrying
.............

I think that you could find out what is the number of Service Center of your SIM, and define it as a modem setting:

smsc = number in international format