I don't know if this is related, but a few days ago i changed my cellular provider and reconfigured fMMS for it.

The 3G and cellular networks are working good, i can send MMS, send/receive calls and receive SMSs, but i am unable to send SMS - although i see no errors, the SMS does not get to its destination.

I tried using smssend command line utility with:

smssend -n [number] -m test

the output seems ok

smssend version 0.1.10
copyright(c) 2011 by Paolo Iommarini <sakya_tg@yahoo.it>
Sending SMS:
[1/1]......OK

and still - the SMS does not reach to its destination/s (so it does not work both from here and the "conversation" hildon application).

An important thing to mention - before configuring fMMS i was able to send a few SMSs successfully (with this new provider), so i thought it might be related to the fMMS configuration so i tried to reset its settings and even completely uninstall it (and restart the device) but still - sending SMS has the same behavior.

How is it possible to debug this?

Have you tried that SIM card with a different phone?

OK - just checked and verified - the problem is with the cellular network provider