I worked at a call center for a few years. I have a moderate stutter, it mostly comes in the form of blocks, and few repetitions. What I can tell you about my experience in that work environment is that you can easily get away with stuttering over the phone. I was able to do all the things that I couldn't do in real life conversations to get the words out. Such as contort my mouth a bit, squint really heavily and ball my hand up in a fist and tap it on the desk. Also, the added luxury of a phone call is that you can put people on brief holds to "look stuff up" while you work through the block. Don't worry about your co workers and management judging you. As long as you are up front about your speech impediment people are usually extremely supportive and impressed by the fact that you are putting yourself out there. What helped me was wearing my speech impediment on my sleeve. I'd often joke about how I was like a fish trying to climb a tree. Good luck friend :) I know you're going to kill it.