Don't let Cell C buy you out of your contract

My debit order of R 350 became R 750 and then R 1550. I specifically said when taking out a data contract that the topping up should be limited to 50 meg yet Cell C decided to make it R 2000.00. I complained about this on the 16th of August and was told it would be resolved in 48 hours. I have emailed and called about 4 times since and no valid answer, every single operator said they will call me back but none did. Now someone in the head office will most likely give me a call and tell me that they will prioritize it and respond on Hello Peter and then nothing will happen again. How long can it take them to find the recording of my contract application?