bad customer servive and broken promises. its ridiculous.

i was promised 2 free phones because my account was charged $15 per line x’s 3 lines per month from august 22- april 23 after I specifically called to cancel it. I was told that as soon as I activated my new phones that the bill would be 0’d out for them. However that’s not been the case at all, I have had to call in every month to have them take these charges off my bill. It’s been confirmed 10 times already and I’ve spoken to person after person and managers always promising the same thing ( that the payments for these devices will be zero’d out, but they never are. I literally have lost so much work over being on the phone for hours and hours. I get anxiety every time I have to call them because this is so ridiculous that it’s not even ok at all. I never get called back from a supervisor like they promise one will. What can I do about this sort of situation? At this point a new carrier seems like the best solution but I refuse to pay for these phone that I didn’t want or need mainly because I didn’t want to be stuck in a 2 year payment plan so I could switch whenever I wanted. But can’t now because they refuse to take those off my account.