I didn't answer my phone for about 4 years. My solution was to force myself to use the phone. I called shops to ask when they would close. I would ask when my energy deal ended. I would say i had a stutter so the caller knew what was going on. I built confidence through repetition. I am pretty confident on the phone now. I still stutter but I don't have much anxiety about it. It isn't a technical solution and might not work for everyone. It did for me, though.