In my late teens I had that problem pretty badly. Even if there were consequences I would avoid making phone calls as much as possible, and very rarely would I answer the phone if someone called.

I can't explain why it created so much fear, but I would just stare at the ringing phone and get tensed up. Afterward I would mentally berate myself for being unable to make myself do it, followed by my parents berating me for having missed answering a call.

Several years ago that fear went away, though I have no clue how or why it disappeared. Phone calls are still uncomfortable, but they aren't fear-inducing. Perhaps it was simply a matter of having done it enough times, causing it to become familiar.