For future reference, as discussed in IRC, the answer is:

check if your upstream provider supports SIP SIMPLE to SMS (SIMPLE being the SIP extension for messaging).

If the upstream sipports SIMPLE, then you can use mod_sms to route messages.

If upstream only supports some other mean (eg: an API) you can use chatplan for calling that API (eg: maybe via curl, or lua scripting or whatever).

sent from my mobile,
Giovanni Maruzzelli
cell: +39 347 266 56 18