Charges for Streaming Devices

I returned 3 Streaming Devices in October 2021. I have a receipt showing that the devices were received (date and time stamped). They were returned because none of them worked and I have never used them. I have been charged for these devices every month since October 2021. I have to call every month to receive credit for the erroneous charges and am told every month that the devices will be removed from my bill. This has not happened and I was just told that they cannot remove them because they are on an installment plan. When I tried to speak with someone higher up, I was told that was not possible. Has anyone else had this issue? I am about to cancel my service because this very simple issue cannot be corrected even though I am promised every month that it will be corrected.