Unable to cancel the expired contract

I took a router contract with MTN during November 2019 and it expired last year in November. I called to cancel it and I was told that I'll lose all my data if I cancel. I was advised to cancel January 2022 as it was December. I've been trying to cancel the contract since morning. They'll transfer me from one department to another. The first time I was on hold for an hour. I had to hang up and try again. They are unable to assist customers that are canceling an expired contract, only if you want to open a new contract. This delay is due to the fact that they want to load another datar and debit me at the end of the month. If I can succeed in canceling this contract, I will never sign any contract with MTN in the future.