Incompetence

My upgrade was overdue and as it was through Nashua Mobile I did it in November before they closed. My account was then given to MTN. When I received my first bill I noticed that there was a 500MB recurring data which I had not requested plus I was being charged for 2 hardware subsidies. I immediately phoned MTN and was told they would look into it, 2 months later and numerous calls and nothing had changed. I eventually spoke to a lady by the name of Ronel who was very helpful Ref *** it was on the 23.02.2015 at 18h05. She told me that she had sent everything through to accounts and would put a rush on it. The following month I was credited for the amounts that were taken off. For the next two months my account was correct. I have now received my invoice due this month and it is back to 2 hardware subsides and the 500MB recurring data. I have tried phoning waiting for 2 hrs continuously - to no avail. I am 60 years old and on a very limited income. I budget for the amount to be left in my account to cover debit orders and charges, and now due to this it will give me a bad name. The difference is well over a R100. I am beyond frustrated. Please help