When using Asterisk, the DTMF is detected and interpreted by Asterisk. If you are having DTMF recognition problems, you can try the following:

1. Set relaxdtmf=yes
In your /etc/asterisk/zapata.conf, set "relaxdtmf=yes", and confirm that relax DTMF is set to yes on your channel by typing "zap show channel N" in your asterisk CLI.
2. Increase your rxgain
Increase your rxgain in your /etc/asterisk/zapata.conf and see if this helps.

3. Check your voice quality
If you have a lot of noise on your line, this will affect your DTMF recognition performance. Try to reduce the noise on the line.

4. Check for echo.
If you have a lot of echo on the line, this will affect your DTMF recognition. Check if you have a lot of echo during calls