cancellation of contract

i bought a contract phone in August 2013 and the contract was suppose to end on August 2015, i called them to cancel the contract and migrate my number on July 2015 and i received an email that they have received my email my contract has been cancelled, since then i have been receiving the airtime and data s and when i call them they say i should pay that amount and the contract will be terminated, but still they haven't terminated it and Im still paying for that airtime and data s, i think this has gone too far because i wont be able to pay for the money that i did not budget for, and i cant be on bad credit records because of their silly mistakes. please help me Peter.