MTN does not respond to e-mail, phone call, and can't even cancel a contract in store. Bad service.

I have been sending MTN e-mails since 6 December 2022 to cancel my contract (sim only contract), and I have had no response. Nobody is able / willing to help me. TO my surprise they deducted a large amount of money from my bank account again yesterday. I have asked 5 times for my contract to be cancelled. I don't know what avenue to take anymore as money is just being deducted from my bank account.