OVER CHARGED WITH DATA USAGE

I Have a cell phone contract with Vodacom but it a split billing account where my company pays a certain amount of the contract monthly. Since I got the contract, I was over charged with data usage because I added 2GB of data to the SMART M contract and also add data as I need at the price that the data bundles cost.<br> <br> Month after month I saw big amounts for data usage which the CCAs and Shop assistants cannot explain to me.<br> <br> I disputed my bill but my line was cut and I have to pay the bill but did not received an answer which makes sense to me. I asked the Representative of Vodacom to change my contract to a Top-up contract and she told me that it was done in December 2015, starting on January 1 2016 but it did not happen. she do not answer my emails.<br> <br> What is the reason for the data usage while I buy data in bundles. The CCA told me about arrears of more than R4000 for deduction from my bank account at the end of January 2016. Where did this arrears come from?