Getting over charged by T-Mobile and not getting any help!

Super frustrated….. went with my mom to upgrade our phones months ago and we went with the Go5G 55+ plan plus home internet and two new phones.

Told we would be paying $144. Three whole billing cycles later and we are still paying $20 more than we should be. And T-Mobile has been charging us randomly outside of our billing due date. Went to a T-Mobile store and even they didn't know what was going on. It's incredibly frustrating because we switched to all of this in order to save money and now we are paying more. And no one can give us any answers.