Contract cancellation

I had a contact with MTN and it was paid off. The person whom assisted me asked me if I’d like to continue using their data and I told her no, I just wanted the phone. My contract should be cancelled. MTN kept debiting my account after I was done with my contract, I gave them a few months thinking maybe my cancellation request is not actioned yet as soon as is actioned they will stop but they never did. I decided to dispute their debits. I called MTN on the 17th of November 2024 and spoke to Gledwin, he told me that my cancellation request was received but never actioned. So someone at MTN did not do their job and now I am held accountable for that. Because apparently I now owe them and my case was handed to their legal team, how? Because I cancelled that contract with them but they decided not to cancel it and kept debiting my account with me approving. Now my life is stuck because of their incompetency, I app**** for apartment last week amd my application was declined because I owe MTN.