Hello, guis!

I'm very glad to be here and I have a small question, if you can help me with an answer, please, please.
I've searched all over (including in this community) about this CMS ERROR: 500 (Unknown error), but I can't solve it out..

The problem is I have 2 SIM cards. One of them is a subscription (monthly paid) at the local GSM network provider (Orange if it is permitted to say) and the other one is a prepaid SIM (at Orange as well). The thing is that I've managed to send SMS's with the first one flawless, but with the very same settings (including the modifications for /dev/ttySxx and pin for there are the differences), the second one (prepaid) does not work at all... The prepaid if I insert it into phone, it has signal, it sends SMS, it initiates and receives calls, has credit, etc., but in the modem it won't send sms with smstools3 as I can with the other SIM.
The configuration for my smsd.conf is:
devices = GSM1
logfile = /var/log/smsd.log
loglevel = 7

spool_directory_order = yes

delaytime_mainprocess = 1

delaytime = 5

os_cygwin = yes

[GSM1]
device = /dev/ttyS9
incoming = yes
pin = 0000

This config sends with one SIM and with the prepaid SIM it doesn't...
It gives the following error:
..
2020-07-20 15:36:15,7, GSM1: Command is sent, waiting for the answer. (60)
2020-07-20 15:36:42,7, GSM1: <- +CMS ERROR: 500 (Unknown error)
2020-07-20 15:36:42,3, GSM1: The modem answer was not OK: +CMS ERROR: 500 (Unknown error)
2020-07-20 15:36:42,4, GSM1: Sending SMS to 0728xxxxxx failed, trying time 108 sec. Retries: 2.
2020-07-20 15:36:42,6, GSM1: Deleted file /var/spool/sms/checked/df7b2cf3-0c22-44a5-8924-d4f305e79ee4
..

In all my testing, I've tried this configuration and as well as the first config, the prepaid SIM does the same error:
devices = GSM1
logfile = /var/log/smsd.log
loglevel = 7

spool_directory_order = yes

delaytime_mainprocess = 1

delaytime = 5

os_cygwin = yes

[GSM1]
device = /dev/ttyS9
check_network = no
incoming = yes
pin = 0001
outgoing = yes
memory_start = 0
#baudrate = 9600
report = yes
rtscts = yes
read_timeout = 5
#init = AT+CMEE=1
#init2 = AT+CPMS="SM"
signal_quality_ber_ignore = yes
#init = AT+CPMS="SM","SM","SM"
#init = AT+CPMS="SM","ME","SM"
#init = AT+CMGF=1
smsc = 40744946000
report_device_details = yes

Almost all the combinations with these above return an error after the message is at the point of sending:
2020-07-20 15:33:09,5, smsd: SMS To: 0728xxxxxx. Moved file /var/spool/sms/outgoing/df7b2cf3-0c22-44a5-8924-d4f305e79ee4 to /var/spool/sms/checked 2020-07-20 15:33:09,7, GSM1: -> AT+CPIN? 2020-07-20 15:33:09,7, GSM1: Command is sent, waiting for the answer. (10) 2020-07-20 15:33:09,7, GSM1: <- +CPIN: READY OK 2020-07-20 15:33:09,7, GSM1: -> AT+CSQ 2020-07-20 15:33:09,7, GSM1: Command is sent, waiting for the answer. (10) 2020-07-20 15:33:09,7, GSM1: <- +CSQ: 22,99 OK 2020-07-20 15:33:09,6, GSM1: Signal Strength Indicator: (22,99) -69 dBm (Excellent), Bit Error Rate: not known or not detectable 2020-07-20 15:33:09,6, GSM1: Checking if Modem is registered to the network 2020-07-20 15:33:10,7, GSM1: -> AT+CREG? 2020-07-20 15:33:10,7, GSM1: Command is sent, waiting for the answer. (10) 2020-07-20 15:33:10,7, GSM1: <- +CREG: 2,1,"03F2","3747" OK 2020-07-20 15:33:10,6, GSM1: Modem is registered to the network 2020-07-20 15:33:10,6, GSM1: Selecting PDU mode 2020-07-20 15:33:10,7, GSM1: -> AT+CMGF=0 2020-07-20 15:33:10,7, GSM1: Command is sent, waiting for the answer. (5) 2020-07-20 15:33:10,7, GSM1: <- OK 2020-07-20 15:33:10,7, GSM1: -> AT+CMGS=111 2020-07-20 15:33:10,7, GSM1: Command is sent, waiting for the answer. (10) 2020-07-20 15:33:10,7, GSM1: <- > 2020-07-20 15:33:10,7, GSM1: -> 0011000A9170829977310000FF6F8D611DF41E87F5E930489F6697D3207219140335727ABACC0295C7E8343C0C1A96DD74799D5D4F83C86510551E76CFCD757DBA0C9A87DDE77ADA1D0609EBE3BABC3CA7A741F630A82E2F87F561D01B0497A7DB617B581E0699E5F5F63B3C0FBB00 2020-07-20 15:33:10,7, GSM1: Command is sent, waiting for the answer. (60) 2020-07-20 15:33:37,7, GSM1: <- +CMS ERROR: 500 (Unknown error) 2020-07-20 15:33:37,3, GSM1: The modem answer was not OK: +CMS ERROR: 500 (Unknown error) 2020-07-20 15:33:37,5, GSM1: Waiting 10 sec. before retrying 2020-07-20 15:33:47,6, GSM1: Checking if modem is ready ...

Could you please help me with an advice, what shuld I do?

Kind Regards,
Petru

The destination number is in the national format, 0728xxxxxx, but by default it should be presented in the international format. In your case this number should be 40728xxxxxx.

First try if the prefix 4 helps. If it helps, you could test national format To: 0728xxxxxx with a header To_TOA: national. Assuming that everything goes fine, you can automate the selection with a global setting national_prefixes = 0. With this settings all numbers starting with 0 are said to be national numbers, and all others are international numbers. For more information please view this: Using Type Of Address selection.