Oh yes, phones are my lifelong nemesis. For most of my childhood I was too afraid to talk to any strangers in person (didn't speak a word the entire Kindergarten year - my mom had to take me into a closet and interview me with a tape recorder so the class could hear my voice!), couldn't ask for help at a grocery store, etc. I still don't like smalltalk or having to start conversations but I can do it, and I'm fine with quick questions.
But not on the phone!

My therapists always have said I'm afraid of making a mistake or sounding stupid, and that may be true but it isn't my conscious thought. I just freeze up when confronted with ANY question or unexpected response. That happens in person, too, but I can't avoid that like I can avoid phone calls. I can order pizza delivery or ask questions of a business or make appointments if I write everything down ahead of time. But I virtually never answer the phone. I also let it go to voice mail. And then I don't check the voice mail for weeks. Oops.
When I was a senior in high school I wanted to be a TA for my kindergarten teacher (who I had never spoken to!). I was too afraid to call her so I had my sister do it. And then my sister pretended to be me and I was super mad. But when I finally did talk to her she said she knew immediately who I was! Guess I made an impression as a student.
I tend to say the very shortest greeting when answering the phone at a job. I'll just quickly say the department or company name. I got yelled at by a doctor at my work for not stating my name when I answer, so now I quickly say "(company name), this is (name)." Ha. And if I get flustered I fail to do even that. I'm so glad I now almost never have to answer the phone at work.
It's definitely the freezing up when put on the spot, even if the question is super easy and normal. Just in the past couple of days I've started to think about maybe taking an improv class to work on that skill in a non-dangerous environment. Intimidating, yes! But I can't get fired from an improv class. Still pondering.