I hate making phone calls. I feel your pain. And you know if you are calling the dentist and the electrician, it can't be good, right?
I had a job where I had to call customers who were not necessarily happy. I was working from home, so I didn't always look professional. But if I had to call a customer that day, I made sure I was dressed in professional clothes and my hair was combed. Also, someone told me to stand up when you make the call. It really does help with the anxiety-producing phone call.
Best of luck. Post when you've made your phone calls.