Repeated Incorrect Billing

I recently switched over to the Red Unlimited package at Vodacom, specifically to avoid the massive surprise charges that they have hit me with over the past few years. I have a limit on my account to avoid getting nasty billing surprises, however, Vodacom pays NO regard for any of this. Even though I have a limit on my account I still have to listen to ******* motivations that \Vodacom will not cut the account while you are using the data". This doesn't even make any sense because the amount that I am being charged is MUCH more than my limit on my account and nobody is able to tell me why this has happened!!! I am fed up with this place just deducting money from my account regardless of whether they have messed up"