Vodacom - canceling cellphone contract for years but still being biled for something I am not using.

I have had trouble canceling my contract with this company. Customer service is very bad where you think you're getting somewhere only for them to end the call and not return it. About 3-4 years ago I called into customer service ( this was an ongoing thing) and canceled my cellphone contract. I recieved a message saying that the debit order was canceled and was reassured on the phone that my contract was canceled/determinated. A month after I was still debited and it occurred for a few months and I would call the customer service only for it to be useless as no one could assist me( this was also an ongoing thing) . I went into multiple Vodacom stores and no one could assist me either. Their response was that they "could not find me on the system" but the company had been debiting from my account after it was "canceled". I then switched banks and the account that Vodacom had been debiting was then in a minus. This has been going on for years. I went into store yesterday only to find out that I am on the old system and the numbers were recycled but I was still being billed (for I don't know what?) as my contract was squared within the 2 year period. I have had such a horrible experience with Vodacom and I am so reluctant in opening up any other contracts.