Cancelled/expired contract ****ming

My contract was expiring on the 23rd December 2024, i called beginning of November to tell them i’m cancelling the contract & I was offered to convert it to prepaid & that i’ll need to pay R100 once off. I was assured from December that will be our new terms. I called back towards end of November to check if contract waa indeed cancelled, I was assured it’ll be like that from December. Instead of charging R100 they keep taking the original amount of the contract.