Social anxiety sucks, but I think the only thing that can really help is exposure therapy and maybe seeing a therapist. For me, I found that just pushing myself is the best way to get through it. I worked a tech support job at a call center years ago and with my social anxiety that was a rough one. My first day I almost quit because of the anxiety from it. It didn't help that a lot of the customers I talked to were elderly people who made mistakes on orders that couldn't be changed. I stuck with it and survived. It was a temp job, but felt like it went on forever. I hated it.
But, I found I did become more comfortable on the phone. I still hate talking on the phone, but it's much easier than it used to be for me. And I think it's because of that exposure to it that helped me.