Vodacom increases contracts without consulting customer.

Vodacom increased my contract billing by R16 without consulting me. When I queried this the consulting stated that in the terms and conditions Vodacom has the right to amend the contract bundles and pricing at any stage and that I have agreed to this. The problem is that I took the contract telephonically and now feel like Vodacom are messing me around. I don't feel valued as a customer. I haven't had this issue on my previous contract.