Charged BIS for Samsung ,zero responsibility taken

I was charged for BIS for 20 months after being shown that it was cancelled on the Vodacom Garden Route Mall store system, it 'apparently' failed to cancel billing on the Head offices system but after over 5 calls to Vodacom customer service, being told that I should have requested the cancellation of BIS(which I did) and requesting I find proof or evidence I cancelled the BIS, (that is on their system which I have no access to) and the promise for a call back from someone in a higher position that will not just follow a script and has the ability to resolve a problem, over 6 months and nothing has been done, even phone calls with laughing staff at my frustration in the situation, ending calls due to uncer*****y of how to handle the problem. For a company that wants to retain my business as I am now at the end of my contract and considers themselves a 'service provider' I am appalled at the service I am receiving.