So elastix 2.0 freepbx 188.8.131.52 and grandstream GXP2000 phones. I have been getting complaints from users that when they call certain numbers the DTMF digit is not getting recognized by that IVR. The phones and freepbx are set to RFC2833 because setting the phones to SIP INFO they cant log into the voicemail. The VoIP provider is set to AUTO and it works pretty good with almost every IVR sending the DTMF digits but certain ones cant detect the digits and sometimes if you push the same digit multiple times it can detect it. Does anyone have any ideas to solve this? Is it the phones and I just need to work on replacing them? The phones do have the latest firmware on them.