Anxiety Support Group
Anxiety is a physical condition marked by intense and persistent feelings of distress, fear, angst or dread. General anxiety caused by routine day-to-day stresses usually passes quickly and is experienced by almost everyone at one time or another. However, such feelings that linger over time and are very difficult to cope with, and which lack a clear cause, may indicate...

I never realized it could be a problem for someone with anxiety, and so I will share what I do.
I write down the questions I have for the reason I'm calling this person. I keep the questions simple. I look at the question to stay calm and focused as needed.
I also have someone nearby to help with the clarity (since I can not always hear what is said on the telephone), and again, keeping your calm and focus up front will help you be able to breathe normally while on the telephone.
I hope this helps. Best wishes.