Request paid up letter

Request for paid up letter. I had a contract with MTN, and terminated it before it could end by paying the settlement amount on my devices. After payment I’ve been trying to get a paid up letter and MTN Credit department are not picking up phone calls. You have to call the contract department and then they transfer you to the credit department. It’s been a week now of calling more than 4 times a day and staying on the line for more than 2 hours each time. It’s very disappointing that when you want to part ways with MTN for their bad service they make it extra hard for you