Vodacom Refuse to Stop expired Contract

I have 3 contract with this provider. I cancelled one of my contracts various times. Everytime I speak to a consultant they confirm they have the cancellation requests on the system and promise me the contract will be closed yet they continue to deduct the contract amount the next month. They are quick to sell you a contract but once it is signed there is no way to stop it even if the contract is expired more than a year ago.