I’m sure this doesn’t work for everybody but when I’m about to stutter on numbers in a phone number I just say “uh” beforehand. Like “555.. uh.. 3751” I can say it quickly enough that it’s not super noticeable and it gives me enough of a bridge word to continue the numbers. Also, there’s nothing wrong with telling the person on the phone that you have a stutter. It’s so much better to say “Sorry, I have a stutter” than it is to just have radio silence while you try to work through a block. I only ever bring it up after I have already had a block, but even just saying that in the past has helped me to be more comfortable and to continue with the conversation. Then you can say something like “the number 4” instead of just “4” and it won’t sound weird because now they know you’re having trouble and trying to get through it. My biggest issue is answering the phone at work and then not being able to say “Hello”. Haven’t found a workaround on that one yet lol Edit: Sorry, I misread the part where you said you were there in person. The advice still works though! Also writing it down works as a last resort if you are really having trouble. There’s no shame at all in that.