MTN PLEASE GIVE ME MY PAID UP LETTER

My MTN account was handed over to legal because I was owing MTN on a contract that I thought it was expired because of the matured contract date. Now I have paid MTN their money and requested the paid up letter but they can't actually provide it. Instead, no one wants to take accountability as my call is being transferred to different departments all the time. It has been over a week now and I have not received any positive feedback on my account. I have also sent emails to legal department which are not being responded to. All I need is the paid up letter.