Refusing to cancel my contract which ended 2years ago

I had contract which ended 2years ago, I have been trying to cancel it but with no help from Telkom , I made numerous call using my airtime and every time I’m trying to cancel they put me thru retention department and I don’t want to continue I just want to cancel my contract and get a paid up letter as they have blacklisted me for not making payments for a contract that long ended and they are the ones refusing to cancel the contract I just want the contract cancelled