Hello. This questions is not specific to FS but to all the SIP Gateways. We currently work with several Voice Providers , including the big carriers BT , etc and this situation happens from time to time and some more frequently then other. We call phone A , the person answers and presses some keys and voila RTP Events Received , all goes well. We disconnect and call that exact phone and DTMF is not working anymore ,... We disconnect the call from another provider and we have again the DTMF Tones. Now we try another carrier and the same situation happens . Do anyone of you guys have anything to say on this a best practice , should i use RFC2833 and in band at the same time trying to catch any missing tones ? Regards Antonio Teixeira