Unacceptable data charges

My bill is never more than R600. In Jan 2015 my phone had an issue where it started to update apps on it own. I tried to cancel the updates, it did not. I tried to power off the phone and then restated it, it still continued with the updates. I took off the battery and sim and this still did not work. I had to force stop something with the help of the Greenstone store. I then received a bill for almost R1300, so I queried this with Cell C and they keep telling me that the charges are correct. If the device had not had not been faulty, the charges would not have occurred. I have had endless issues with this phone and Cell C would have this on their records. I want a refund of R600. I now understand why the banner was put up.