I'm the same, even for ordinary phone calls. I try and bribe myself with nice things to do after I make all my calls, and set aside a time specifically for it. When I was going through a lot of life events and had the similar situation of having to make lots of calls I didn't want, I did it gradually. So I rang an automated service (thing that tells you the time), just to get used to calling. Then a nearby store just to ask their opening hours. Then a really good friend for a chat. And then I started with my business calls. It was still hard but not as bad as I feared. Just getting some of the stuff I needed to start doing was such a good feeling (back in control of my life) that helped too. Good luck, I know this isn't easy!