I have such a hard time with phone calls!! I can relate with everything written on this thread... Here's a golden tip for everyone: Don't give yourself time to think! The more time you give yourself to think about answering a call or making a call, the more negative thoughts you will come up with. Answer calls the second you hear a ring, no hesitation. When you want to make a phone call, first just determine why you want to talk to them (you may want to know something, or are just curious to know how they are doing). Figure it out and pick up the phone and dial. Don't give yourself time to think about anything else. Figure out why you want to call, then BAM start dialing. Listen to what the other person says, think about what it means to you, and then respond.
By the way, I'm not trying to make it sound like this is all so easy to do. Please believe that I can relate with what you are all saying. This will really help you. And, after a while, you will realize that you have less anxiety about answering phones than you used to.