None cancellation of contract by vodacom

I had a two year contract with Vodacom which expired in February. I called in February to speak to Sphiwe Mthimunye who informed me that the contract was still continuing which is why they kept on deducting from her account. She was provided with a reference number *** and that the contract will be cancelled. I stayed for more than 30 minutes and he kept on asking if I am still there and he cancel the contract. I noted the deduction again called Vodacom spoke to Phindile Twala and said my contract is not yet cancelled but its on the process. Now Vodacom is telling me that I owe them R660 the contract is still active. My intentions was clear when I called Vodacom to cancel the contract since two years has since expired. Vodacom must cancel the contract as I paid until the expiry of the contract