I'm sorry you're suffering. That's really rough and I'm sure it's extra frustrating being in a service job where you're seeing a ton of people all the time and for very brief encounters. I've been a stutterer all of my life (I'm 35 now). I've honestly never felt like a specific therapy has helped me in the way that I really want, which is to just have a silver bullet fix. But if course that's unrealistic. The thing that I'd maybe recommend because it has other wellness effects is looking into meditation and/or yoga breath techniques. They have other health benefits but one of the biggest things with them for me is helping me to manage my anxiety around my speech. Just remember that we are our own worst critics. No one else thinks it's as big of a deal as us because we're always front row center and we always imagine it's worse than it is. People don't care. They really don't.