I'm testing out multiple sms providers, and I'm using the api to do reads for reporting on the back end, but I can't seem to figure out how the system knows which sms provider sent a particular sms. The Activity table doesn't seem to have provider_id reference of any kind unless I'm missing it. Is it in an attached table or something? I can't find a list of providers either. Is that in the database?
It looks like you might be after the sms_provider_id from the civicrm_mailing table, or sms_provider_id from the civicrm_action_schedule table.