Been dealing with months of billing / customer support nightmares after cancelling service. Routes for legal action?

This is the worst experience with a company ive ever had.

I had cancelled my service in September 2024, returned my equipment shortly after and was told everything was good and nothing else would be needed. A couple weeks later I received a new statement with a new monthly charge, and have continued to receive a new charge for the last 4 months. 

I’ve had at least 5 different calls with customer service, all at least 1 hour long, with them digging through the “issue on my account”, and them each time assuring me that the issue is resolved and i don't have to worry about anything new. However, each month i get a call from their payment collection team which leads to the same hour long conversation and “promised” resolution each month.

I don't know what to do anymore. My last call the guy literally promised me i wouldn’t have to deal with thus anymore and the balance on my account would vanish but its been a few days ad nothing has changed. I feel hopeless and i don't know what else i can possibly do to help myself, so exhausting for literally no reason or fault of my own.

No idea what i can even do anymore and it seems taking legal action is the only possible way forward since each of the multiple times ive been told the issue has been resolved, nothing has changed at all and i have to continue deal with this mess.