I regret the day I took MTN contract!!

I took a sim card contract with MTN and the contract term ended last year, 2022 August and I called to cancel the contract. The following month I received an invoice and the contract was not cancelled,I then called MTN again to enquire and sent numerous emails they told me there was nothing they can do, I Must just pay the money. What pains me is that I don’t use the sim and I don’t even know where it it.Right now my credit record is tarnished because of that contract.