Theft by Cell C

I had a contract with Cell in 2018 of which the contract was paid up and completed its term. In 2018 they were still debiting my account, of which it cost me extra bank charges to put a stop on the debit. Of which Cell C did not reimburse me for. Now in 2020 again they are debiting my account for which I do not even have an account with Cell C, this is theft and they refuse to refund me. Instead, they expect me to go to the police station and get an affidavit. They shouldn't even be keeping my personal details after my account was closed. Worse is that they are *****ing money from my account, and no one seems to be bothered to sort it out.