Need help!

Vodacom advised me that I am one of the first customers to be transferred to the new system, apparently they have not yet worked out how I can keep track of how much data I am using per day.That means they can send me any bill they wish and I cannot dispute it! I am too scared to use my phone in case a massive bill comes my way! The manager at Alberton city could not tell me when this will be resolved! I need this to be resolved asap I am stopping my debit order!