I've had tech services try to figure out, and I've been back to the Verizon store 4 times, where they have readjusted DTMF tones and even replaced the device with the same issue. Since I use the phone for work and have to call into many teleconferences with access and moderator codes this is a major issue. I'm ready to return the phone, and I waited a long time for it. Otherwise I'm having no issues--but one would think basic phone functions would work in such a high tech device.
It took me a while to figure out that my Blackberry settings couldn't be read by Android. I had to reprogram all my contacts with extensions, etc. I did get my voicemail setting to work correctly. Just initiate the call and all the inputs happen automatically. Sounds like you may have a different issue though.