Unable to cancel a expired contract

My 2 year contract has ended last year and because I'd prefer not deal with Vodacom due to poor service I do not want to upgrade or continue my contract. I have been to 2 different branches to assist me with ending my contract and have been on several calls with customer service. I am still being deducted the full amount of a device I have fully paid for. Won't recommend Vodacom as a service provider.