Notification of increase in subscription

I received notification from Vodacom that my subscription will increase from R299 to R319 per month. I signed a contract with Nashuamobile, and this was recently migrated to Vodacom. If my budget no longer works and I want to change my subscription, I have to buy out the contract at the full price. <br> <br> I have sent communication to Vodacom, as this is not acceptable to me. I have to fullfill my contractual obligations, and I feel Vodacom has no right to simply increase subscriptions. My contract only expires in July 2015. I do not care whether or not there was no increase in the past or whether their budget does not work.