Appalling service

I app**** for an upgrade in September, but instead of processing an upgrade, Vodacom put it through as a new contract. I only realised months later after noticing that we were being charged double. I have been trying for the past two months to rectify this. Vodacom refuse to acknowledge that it was there fault, so I have accepted that this is not worth fighting. But now I can't get the cancellation actioned. Every week I have to phone Vodacom who assure me that the phone and watch that came with the new contract with be collected and the new contract cancelled. Nothing has happened except that we continue to pay double. I don't know what to do anymore. (Ref: ***)