I've always hated talking on the phone too. I adopted text messaging happily when that came out.
Here's how I make a phone call when I have no other option. I work what I am going to say first. Once I comfortable with that, I will stop thinking about the phone call. Just distract myself with something.
When the idea of the phone call pops into my head again, I just make it immediately. If I think about it too long, I'll get nervous. If that happens, I just distract myself until the idea of making the call pops into my head again.
For me, the trick is to separate prepping for the phone conversation from the call itself. The conversation takes thought, but the call itself doesn't take much. Doing it this way is slow (sometimes a couple days before I actually make the call, often a few hours, sometimes just a few minutes), but it involves a lot less anxiety for me than combining the mental preparation and the call together.
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RAADS-R: 176.0
ADOS-2 Module 4: 9 (Autism Spectrum)
EQ: 7
AQ: 35
Diagnosed with ASD Level 1 15 Jan 2016