dissapointed

I had a contract with cell c from June 2016 it was a 24 months contract was supposed to end June 2018 but still, they keep on deducting money on my account when I go to the bank to reverse it they phone and say they will hand me over how so. the worse part they didn't deduct month-end July but deduct month end august how possible is this? please help me cancel this and clear my name before is too late whatever they say am owing them I can settle it as long as they can cancel this contract.