Ask HN: How can I be less awkward on phone calls with vendors/clients?

I recently became a product manager, and my job includes talking to vendors / potential vendors, and the occasional client. I've always had a bit of phone anxiety, but I have a particularly tough time "being smooth" on phone calls with professionals I've never met.

I try to start with a brief introduction of myself (how long I've been at the company, what my focus is, etc), but sometimes I speak too quickly or not clearly enough. And because I don't have any visual feedback, I sometimes don't know whose turn it is to speak.

I'd really appreciate any advice on how I can be better on phone calls. I think I'm getting a bit better with practice, but I'm still stumbling over my words and finding that I'm much less clear over the phone than in person with coworkers.