MTN refusing to cancel my contract

I took out a cell phone contract with MTN back in 2019 and my final instalment was supposed to be at the end of November 2022, they kept on calling me before my final instalment, trying to get me to upgrade my contract and each time they called I let them know that I am not interesting in upgrading, and that I want to cancel my contract. I must have been ignored each time because I am going to get debited at the end of this month.