For me, I was afraid of what would happen if I called people, like annoying them, calling at tha bad time, wrong numbers, having someone else pick up the phone, and either A)having to ask for them B)getting nervous and hanging up C)saying something wrong or D)confusing them witht he person I was trying to get a hold of.
After a while I would put off calling people, and would cancel plans because of it. But it helped to have someone else dial the phone, wait until it started to ring, and then give it to me, which in a way placed on me an obligation to wait until someone answered on the other side. Pacing actually helped, and many other things. I just took it step by step.