When I have to deal with strangers(usually I'm the customer though) and I'm anxious about it. I have a technique to decrease my anxiety. I have a very well rehearsed upbeat "hi, how are you?" I'm confident I can always say. Usually the person you are dealing with is taken back by the positivity and even if you do stutter after that they are way more patient and happy to listen to you. It makes me feel better so I stutter less and if i do stutter they are usually much better at listening. Maybe give a go and see if it works for you