That’s a hard one. My stutter is relatively mild and doesn’t interfere too much with my speech when answering a phone unless I’m asked an unexpected question. I usually develops a script at least for my opening line “Thank you for calling (insert name of business), how may I help you?” . At my current job, everyone would answer the phone by just saying “Shop name”. But I brought my script from my previous job because I can’t say our shop name without a stutter (Starts with a C, bad one for me to open with.) so saying “Thank you for calling...” first eases me into our shop name. Bonus- a few other coworkers have started saying my spiel! As for general speech with a phone.. my Mom was a secretary and I witnessed her phone voice. I hated it and always said I’d never develop one. Well guess what? I have one. It’s sugary and sweet and kinda sing-songy which cuts down on my stutter (you don’t stutter when you sing! Different regions of the brain!) . It doesn’t solve it completely but it helps.