increase in monthly subscription

I have recently taken out a contract with Vodacom, and to my surprise on my first months statement states that my monthly subscription will be increasing due to Vodacom running upgrades.I have signed a fixed contract and to my knowledge that is the amount I would pay. I have went through the documentation that I was given and i cannot see anywhere on that contact that it allows the service provider to increase my contract. this makes me worried that the service provider can now debit whatever amount from my account as they have the right to. as a consumer where is my rights????? what protects us from this ********ness??? i called the 082111 number and spoke to Felicia Faku, who said its part f the t/c , when i asked here where about is it she put me on hold as she doesn't know herself, i then spoke to her manager Phologo who is a WASTE OF A MANAGER AND DOES NOT KNOW WHAT CLIENT SERVISE IS!!!! i explained to him i did not get any t/c booklet when i signed my contract. i asked him to get a copy and for me which he wants docs requesting. i will no send any docs as the was a mess up from Vodacom. I DO NOT ACCEPT THIS INCREACE IN MY SUPSCRIPTION FEE! all i say is Vodacom SUCKS