MTN - Impossible to cancel contract

If I could I would give MTN a zero rating. I have been attempting to cancel a contract that has expired in September 2021 already with no success, in the mean time I have stopped all of my debit orders with my bank and MTN has only been sending be the piled up bills with treats of black listing me. I have listed my grievances with very limited replies from MTN and with no resolutions in sight. If there is anybody that can assist me I will be very greatfull as they have cut their services to my other contracts that are still in place.