What number do I call in order to change my plan and turn off mobile hhotspot?

Our internet went out recently, so we changed our plan to include mobile hotspot till it was fixed. Everything is fine now, but I don't know how to change my plan back to it's previous state.

I can't figure out how to use the myATT app, so I'd prefer a number to call. I know I called them to set it up, but I can't remember the number I called.

I'm a daughter trying to help my mother (whose name is on the bill) So any help is appreciated.