Cell c and i phone data

First we went to Goldfieldsmall to ask help with an i phone that is using way to much data. Just to be told that they dont know iphone. Chewing gum from welkom to cairo. Not helpfull at all! I have phoned the cell c callcentre asking them for help. What is taking all the data? After being transfered three times on the last call to them, i was told that i would recieve an sms in five minutes with a ref nr. Still waiting. They all keep going to the system saying they cant see where the sites is that uses the data. I understand that. I keep saying, we have turned off almost all the cellular data connections. Two pho es. One used 1100mb and the other one 400mb in the sametime, with exactly the same settings as far as i can see? Phone uses wifi during the day?