5 months, no service!!!

In the month of May, I called MTN direct to upgrade my cellphone line. At the moment I had 2 packages with them....a unlimited data package (which I use for downloading) and my cellphone contract. MTN then upgraded my data package instead of my cellphone contract! My data package was switched over to the 350 package that they currently had, which resulted in a high cellphone account. I contacted them, and they said that its their fault, and will credit my account back. I've been waiting for 5 MONTHS now, and noting has been done. The call centre's people tells me all the time that it has been escalated to accounts department. My cellphone account gets suspended every month because of that outstanding balance which MTN is liable for!!! At the same time, I do not have internet access anymore because of their wrong upgrade that was done, and have to buy data on a month to month basis!!! Ive been with MTN since I can remember and this is how they treat a loyal customer???? Never missed any payments!!! Very poor service!!! Thinking of changing to another network just so that I dont have to deal with MTN anymore!!!!! TOTALLY DISGUSTED in their service!!! U suck MTN!