@Rommel @zyf I checked with my team the feature has been picked and we are evaluating the possible solutions .
there are generally three methods for sending DTMF tones:
In-band (this is what we do, sending the button frequency over the audio wire)
2 different out-of-band methods:
RFC 2833/4733 - send digits as non-audio RTP packet
SIP INFO - send digits as SIP INFO requests
RFC 2833 is the default that most people use. an ideal implementation would have all three and/or configure which one for each call.
twilio doesn't support RFC 2833 over bidirectional streams. they'll want to use elastic sip trunking in twilio to send calls to our SBC and then DTMF will work
SO, if you as a human can call the number and your dtmf tones are working BUT when bot calls and sends dtmf it's not working, THEN most likely they use our SBC