I completely understand the feeling, I speak the worst over the phone and on my online meetings, and at times it can get stressful and physically grueling. The thing that helped me is of course is writing down some notes before the call along with “reminders” that I’m allowed to stutter and that my goal is to get things done - while stuttering. Another thing that helped me is making a call as soon as I wake up or as soon as I finish with any activity that I was occupied with. That way I don’t put much thought into the call itself that usually gets me into super panic mode. It also makes me feel like I have control over my actions and not the stutter. I also walk around the house while speaking over the phone to help me relax a bit.