I have worked customer service for most of my working life and its been tricky. I have had a couple of people who were super rude. It had helped me to shape my character, and I did meet a lot of people that were compassionate and understanding. It really depends on the person. Don't be discouraged by other people. It's good to know your rights, google "ADA and stuttering", there is some information on what to do if you are openly discriminated against. You can't fire someone for stuttering.