Thousands charged for data not used!

Cell phone contract with BIS. Since December 2014 additional data amounting to thousands of rands has been charged to my phone. Complaint lodged with Autopage Sunridge Park, phone handed in to be 'wiped'. Received phone back, data again charged when nothing had been downloaded despite the technician saying nothing was found on the phone. Service suspended as I refused to pay for additional data but paid for normal contract fees only. Mysteriously data used AND charged on a suspended service!! Autopage have not responded to numerous requests for proof of websites data has been downloaded from. Needless to say will never have a phone with them again and will tell all my friends the same!