GAMMA is expecting in the contact header to be formatted in this call example as <sip:[email protected]:53848>
The Contact header advises our SBC where to respond to. If this is a LAN address, or some other address which you’re not expecting traffic on, the 2-way dialog will be disrupted and calls will not setup correctly.
We would recommend ensuring the Contact headers are amended accordingly and re-testing.
After re-reading your post I don’t really understand what your provider is asking. You’re having trouble with inbound calls, and on an inbound invite the contact header is being set by them, so unless you’re mangling it up (with the rewrite_contact option, which seems to be disabled) then it’s on them to set it properly.
If you need to set the contact header for outbound calls that you initiate from your PBX, you can put the user part in that “Contact User” field, for example your own DID.
I had been thinking the same with the “Contact User” without any luck.
However, I installed the FreePBX v15, and I did a test enabled and disabled the “Rewrite Contact” and in both scenarios the GAMMA trunk work great, I will do other labs in the FreePBX ver 13, and compare both PBX.
Well finally the problem was with the Set up in the NAT in FreePBX v13 in “Asterisk SIP Setting” n the section “Local Networks” I added the public IP of Gamma there, and start to work with out any other parameters. This is tricky because only start to work after restart all the server.
However in FreePBX 15, I did not set up nothing there.
Now it is under control.