Cell C is a ****

I regret the day I decided to take a contract with cell c. My contract came to an end but they still debited and mind you I bought that phone for someone and they lost the phone with the Sim I continued to pay until the it ended they still debited when I stopped the debit order they ruined my credit score reporting that I did not pay...I am completely disappointed and dissatisfied with how cell c handles things!! How can they allocate data in a Sim card that is inactive mxm