most will probably say it's easier to learn sign language than to voice train
Me when I can't figure out fundamental frequencies and spectral rolloff so I study directional verbs and locus indexing
at some point I considered getting a necklace with a bell on it to so I can get people's attention
I got one of those voice amplifiers for work because my normal speaking voice is okay, but yelling is Out Of The Question.
Other way around for me, my normal speaking voice is unheard, but my yelling voice is way too loud and aggressive.
This happened to me too so here's what I say - roll with it. I think if you look at it from the right angle, it's incredibly comforting to know that you don't have to talk and they're cool with it, even if it is a bit awkward.
CW - transphobia
I don't know what kind of store it is for you but it happened to me at a sandwich place, and if I had a bad experience somewhere else where I felt judged because of my voice it was really nice having a safe backup place to fall back to when I needed it.