Be honest about your stuttering but make sure to reiterate that you will not allow it to affect your job performance. I'll give you an example: Something affecting your performance would be not answering enough calls because of your stutter. Something not affecting your performance is stuttering periodically. Do not allow your stutter to restrict your goals and aspirations. I've worked adjacent to these positions and metrics are a big thing. Look into tools such as written scripts to help with the flow of your speech and to lower your average handle time (a very important metric). This metric basically defines how effective you are at routing calls and handling customer issues. Accept the fact that you will have bad days sometimes but again, do not allow it to affect your performance. That's a choice that you make, irregardless of your stutter.