Mitel 3300 - SIP trunks - external call inbound to an extension, should be twinned i.e. calling back out to a cell. The signaling is working, it does ring the cell but no audio. Talking with SIP provider, the Mitel is sending an UPDATE message trying to make the provider hairpin the audio for the two calls together. The provider expert said we need to change settings on the PBX so the PBX bonds the two sets of audio streams itself - which I agree with. Our office PBX (different brand) does exactly that and works properly. I've looked all through the SDP and header options. I'm sure I'm just overlooking it. Basically I need to configure the Mitel PBX so it handles the bonding of the audio between the two calls. Normal calls in and outbound work fine. Thanks for whatever help anyone can provide on this.
