MTN ****MED ME!!!

I am very disappointed with MTN SA. I had a device contract with MTN. I failed to pay for few months and My account was handed over to Nudebt and my device was blocked or blacklisted due to non payment, I then pay the outstanding amount in full. A paid up letter was also issued, but my device is still blocked. I have contacted both MTN and Nudebt, but they keep referring me to each other without resolving the issue. Only today I am being told that they cant unblock my phone because I failed to pay. This is frustrating and unacceptable. I am now stuck with a device that is not working and my money is gone just like that . MTN is a ****!!!!!