I have problem with iPhone. DTMF values are duplicated. I found many topics about this subjet but without any serious response. How to fix this bug ?
My version of asterisk is 13.21.0 and I use OVH trunk (french operator). I tryed with g722 auto and g729 inband but nothing change.
The iPhone is not using a SIP or IAX client I assume?
How are you receiving calls from the PSTN?
iPhone originate the call (from any operators). Asterisk receive the call from OVH trunk, by SIP protocol.
You would need to have your trunking provider troubleshoot the DTMF at their gateway then.
Capturing a call using tcpdump and examining it with Wireshark may yield some clues.