Sorry dude. I’ve been in the same situation many times. I always just avoided saying the word or put “Uhhh” or “Ummm” in front of it. If you can’t avoid it, then tell your boss you literally cannot say the word and ask if you can say something else. I have quit jobs that required me to answer phones. Restaurants are an exception because I could usually be short on the phone. Shame is the name of the stuttering game. As an adult,all I do everyday is try to work on my positivity. Its helped me a lot to think positively and have daily verbal positive reinforcements.