Operating system name and version: Debian 7.7
Version of smsd: 3.1.5
Smsd installed from: sources
Name and model of a modem / phone: Huawei USB Stick
Interface: USB

with my carrier to retrieve my credit on the sim, I have to call 404 and then I'll receive an SMS with credit.
Calling 404, carrier drop the call immediatly, without answer and without hear free line tone.

In this case, SMS3 will not detect the disconnection, wait the timeout, but not delete the temp file in spool folder, so it will call indefinitely the 404.
For outbound i have setup only this paramenter:

voicecall_ignore_modem_response = yes

and in message I setup TIME:18

Let me know.