Was given front end shift, even though I have stutter and don’t know what to do

So I was recently hired for ship from store and during my interview, I asked the assistant manager if I would ever ever have to be on front end or be cashier because I was really worried about it with my stutter and I know I wouldn’t be able to do it. She told me that they would never make me do that if I didn’t feel comfortable.

Earlier this morning, though, I had to talk to my stores manager about my schedule since I’m new and didn’t know when I should be coming in or not and pretty much in two weeks manager put me on four front and shifts that aren’t even in my availability

I’m worried about if they say that I’m gonna have to do it even though I literally can’t and I’m worried about losing my job. So they put me on even though I can’t do it and it’s ours that wouldn’t even be able to work for me.