MTN refuse to help termination of expired contract

Please help me, I have a contract with MTN that have expired in May 2020, now I need to convert the number back to prepaid, and MTN is not willing to help me. If I phone the call center then they ask to motivate my decision, but the cancellation department is not willing to help me. MTN is really a bad company, beside their horrible network that keeps on dropping calls, their services is even worse. Amazing how quick they take your money, but when they must deliver they don't