Still waiting for answers Cell C

I have downgraded on my contract given 30 days notice, effective 1 July. June I was given my balance 100min, 100sms, 1GB Data. Now Cell C said that I have used my data which my monthly payment end of July is nearly R600.00. Moses Mo***eng did call me and mentioned that according to the system the costs was due to data used in June, which I do not agree I had 1GB of data for the month of June and did not finish this as I check my data usages on a regular basis. I need itemised billing emailed to me and answers in writing. I have sent numerous emails and still waiting.