Sending DTMF tones not working

If I call from my voip phone an IVR and I press keys, nothing happen.
I configured DTMF tones as RFC2833 in my phone setting.
What I have to configure in asterisk/freepbx in order to accept DTMF tones?
I use a Betamax provider as outgoing trunk.

You could try inband as DMTF, that worked for me!

For Asterisk, dtmfmode in sip.conf. For FreePBX, ask on the FreePBX web site.

Inband will only work with minimal compression, e.g. G.711 (A-Law and mu-Law). Most high compression codecs, e.g. GSM and G.729 are designed for voice only and will not transmit tone pairs accurately.