How do we get out of a Vodacom contract?

I called vodacom to inform them that I am cancelling my contract when it comes to an end, i requested proof of cancellation but was told that they cant send me proof. Now they are telling me that i owe them money and they have handed my account over to lawyers. when i call them they just give me the run-around. how is my account in arrears when they have not even debited my account. now their lawyers are saying i must give them proof that i have cancelled the contract. how do we get out of this network????