[SR-Users] additional user data for SIP gateway usage?

Hi, I'm after advice. I'm developing a script to provide a degree of PBX functionality for a small to medium office using Kamailio & SEMS. This includes mapping internal extensions to external PSTN numbers via the SIP trunk provider. The incoming mapping is easy using the db_alias functionality. The outgoing mapping is more difficult as the SIP trunk provider requires both the Full National Number and an account number matching the FNN in the outgoing From header. I'd appreciate suggestions on the best way to store, retrieve, and manage the additional information required for outgoing PSTN calls. I think avpops will work but is there some other way to do this? Thanks,