How do I change payload type in freepbx?


I have a problem with incoming calls to a trixbox pbx, the dtmf doesn’t get to the pbx but is carried out properly by the ISP (sip trunk). I work for the ISP and we have had similar problems with other clients and it has been because of the use of a different payload type for RFC2833. In those cases the client has changed the payload type modifying the appropiate parameter in RTP.C file, but in this new case the client has trixbox 1.2 and he doesn’t know how to make the adjustment. I need to indicate to our client how to adjust the payload type through freepbx and honestly i don’t have any experience with freepbx.

I would appreciate if someone can tell me how to adjust payload type through freepbx.

Thanks in advance.

Johan Puentes