I have the same tendency... I find it a lot of work to hold a conversation even with a friend–my mom is pretty much the only person I can comfortably have a phone chat with, probably because she has a very loud, clear voice and because she isn't unpredictable. Calling strangers, or answering a call which I think is from a stranger i.e. my phone/Internet provider company, is stressful. I'll put off phone calls as long as I possibly can, although I'm not sure if it's because of the anxiety or just because they're more time consuming than writing an email.

I've been working on this by forcing myself to offer to make any necessary phone calls at my current job (at the hospital). This is stressful because a) it's usually to strangers, i.e. a patient's family, a doctor, or the X-ray department, and b) it's in French, my second language. The act of saying "oh, I'll take care of that phone call for you" is both easy and rewarding, because I like being really really helpful, and then once I've said I'll do it, I'm committed and I have to do it. Weirdly enough, I'm still scared to answer the phone at work.

Disliking answering phones is part of a long list of semi-phobias I had as a kid–ordering food in restaurants, going up to the checkout to buy things in stores, etc. I still get anxious ordering drinks in a bar. It feels like this is part of the same category as my phone-phobia.