Vodacom Contract - Do as they please!

I upgraded my contract as Vodacom sent me request saying due for an upgrade WHICH I SHOULD never have done! A month later I get billed an extra R438 for a promotional Data Top Up they added to my contract WITHOUT my approval (which I didn't even know was there as we have Wifi at home and at work) They would not reimburse and now Contract goes up by R200 without letting me know or consent. What I get back is this:

Please note that your subscription to the Service constitutes your acceptance of these Terms and Conditions. Vodacom reserves the right to modify the Service(s) where reasonably required, and may from time to time expand on these Terms and Conditions. You will be bound by all current Terms and Conditions.

What is the purpose of getting a contract if they can increase when they like? What about the people that actually have budgets?

Is there anyway to get out of this contract??? I am over asking why my Bill is a different amount! Even though I had requested a cancellation a month after receiving the upgrade with no response! Unfortunately life is busy so we cannot run around or sit on a phone and follow up constantly!

If at all possible.. STAY away from contracts!