Breach off contract agreements

i signed a 2 gig contract for R99 for two years.Earlier today i received an email saying that the contract will increase by R10 on the 1st of May.Vodacom have breached contract agreements in actual fact i should be able to cancel my contract as they are breaching contract agreements.i have two contracts and both are increasing.according to the call centre agent its in the terms and conditions off your contract.as my contract was upgraded over the phone the sales agent has not explained anything off that sort to me.Very disgusted cant wait for my contracts to end with vodacom.