Out-of-bundle data charges

Vodacom has billed me three months in a row for out-of-bundle data that I have not used. I always have a bundle. As soon as I receive the message that my bundle has been depleted, I buy a new one. And at home I am on wi-fi. I was charged R614 for August, R452 for September and R96 for October. None of which I used because I always make sure that I have a bundle.

I called Vodacom and told them that there was something wrong and that I did not use any out-of-bundle data because I always make sure I have a bundle. They told me that after an investigation their conclusion is that my statement is correct. So I am wrong. This is a total of R1162 that Vodacom has ****** from me and do not want to give back. This is unacceptable. And I know I am not the only one that this is happening to, so how can a whole bunch of people be wrong. I want my money back!!