Unable to cancel contract

For the last 3 months we have been trying to cancel our Vodacom contract. When calling the call center you get directed to operator after operator with no-one really being able to cancel a contract. this contract is now past 2 years. When you do eventually speak to a operator you get told to first pay this and that which we went to pay just to hear that you now also have to pay ahead to can cell a contract that is already past its due. the emails are there to proof this. i will not pay this contract any further