I agree with the other replies and would like to add that it’s always okay and often a good idea / ice-breaker to be upfront about stuttering when talking to someone new, especially over the phone. A simple “just FYI, I stutter” after both having introduced yourselves would do. Everybody understands and will take their time to listen, if they know. It alleviates the stigma for both you and the other person. What do you think?