SmartData added

I received my statement and was horrified to find R750 added for SMARTDATA INTERNET. It's only ever appeared 3 times on accounts but for small amounts. I have a locked account and buy data as and when needed. I check often to see what data I have left. When I lodged a query I received an email with a 64 page data report that makes no sense whatsoever and just one sentence in the email. Here's your data report. Really? I have WiFi at work and really hardly ever search or browse the internet at home. Last month I had to call and increase my limit on the account to buy a data bundle, but CellC can add almost R800 to my bill! I have a contract that says 200 min, 200sms and 200MB data. Locked at R1000 but now it is almost R1700!!! I can't afford that. I wanted assistance on how that is possible. Even this month I have data left, and I haven't done anything different?? I need to know how something like that happens. What the hell is Smartdata? I haven't added anything to my profile. When is it used and how? Does my phone automatically use it? I get sms's warning me that my data is depleting - then I buy bundles and I watch them like a hawk. Please help.