no notification of expiry of contract

So I took out a contract with Telkom in December 2014 with a monthly repayment of 269... apparently the contract expires on 11 Dec 2015 but telkom never sent me a notification that the contract was expiring. That being said they have now changed my contract without my consent and are now charging me 700 bucks and no one in the call centre is able to assist me. I logged a query over a week ago and still no feedback. If my contract has expired should I not be the one making the decision of I want to stay with telkom or not? Surely they can't do as they please. This is ********* and *******. I want my contract cancelled ASAP.