BAD SERVICE without any Help

I cancelled the contract in Jan 2023 and i called today and its still not done. every month my account is in arrears, and they switch off my phone due to outstanding amounts for a contract i cancelled in Jan 2023 on the phone with a Call center agent, every month i phone everyone says they will cancel it and still not done I'm now fed up Phoned 13 Jan 2023 at 15.47 i told the guy over the phone to cancel the contract and he said he will however change it to a month to month contract 13/2 phoned to cancel 15/3 phoned to cancel 16/3 phoned to cancel 6/4 phoned to cancel 14/4 phone to cancel 1/5 phoned to cancelled 6/5 phone to cancell 11/5 phone to cancel 29/5 phone to cancel and today 12/6 still not done