Data bill sky-high with no explanation

I received a notice in December that my data bill was high. It started on the 14th of December and my data usage keeps being excessive. I can accept that this is possible if I had done anything different. but I haven't. I made several calls to the vodacom helpline, and they said I must optimize my data usage on my phone and I must take the phone to a vodacom service shop for them to check where the data is being used. I took the phone to the Musgrave Ctre Vodashop, but they said there is nothing they could do. However, they gave me a number where I had to book a data query. This was done about 2 - 3 weeks ago and I have received nothing. My cellphone bill is climbing through the roof. A call centre agent has given me a step by step on what to change to make sure that the phone is optimised. The person at the Musgrave centre suggested that I stop paying until Vodacom can prove how I have used the data, as this is a contravention of the consumer protection act. I checked and I believe it is true. You cannot be charged for something that Vodacom cannot prove you are using and what it is being used for. I am doing nothing different from the past 5 years....!!!!