Poor service provider

I paid up my cellphone contract earlier than the initial date (7 months early). I never missed a single payment or had insufficient funds when they were still debiting. However, MTN decided to ruined my credit score by informing the credit bureau that I missed a payment. And now when I demand my paid up letter, they're telling me that I need to wait for 21 working days. They **** about me missing a payment, and instead of fixing this problem, they're telling me that I need to wait for 21 working days. If you don't have any account with MTN, I suggest that you keep it that way. Otherwise, you'll have endless stress.