Over charging and assistance

In January 2015 I went to upgrade my Data Contract at Selcourt Towers Rene informed me that I would not be able to down grade so I took a My Choice 2GB contract with a R1 limit which means after I have finished using the 2GB of data may data bundle should stop and I would need to load additional data for me to be able to use internet. But to my surprise when I got my account at the end of January my bill was R 1 798.42 but this was not the end when the February bill arrived it was even worst R 3 449.91. I then went back to MTN Secourt Towers to query the account this was in the middle of February I am still waiting for a response. I have phoned and visited the shop a few times and every time they tell me that it's at the billing department for correction and they will get back to me as soon as they have a response. Buit my issue is I will not pay these accounts until this is sorted and the next account is already due again wonder what suprise is waiting for me this month. At the moment I have the Cell Data disconnected on the Tablet because as I explained to Rene I have ADSL at home so I don't use the Cell data as much.