Good bye Vodacom

I have a 24 month contract with Vodacom. Received a sms that my subscription has been increased. Vodacom has a one way contract. They can increase the price without taking into consideration that I signed a 24 month contract that suited my budget. Should I have to cancel the one way contract with Vodacom they will keep me to my part of the contract and make me pay a cancellation fee. Most deffinetly not renewing my contract when it expires. I have a small contract plan. Every drop fills the bucket, and I'm sure a lot of people will not be renewing contracts. Could the increase not be done on NEW contracts?? Vodacom can not be trusted. Good bye Vodacom......