Inconceivably useless service, failure to cancel contract two months in a row, while still charging me for the contract

After having had a Vodacom contract for around 9 years, I went into the Vodacom store in Cresta on 7 September 2018 to request that my account be moved to prepaid (I'd been paying for an upgrade for a phone that I never collected and it was just crazy expensive). I submitted the required documentation, and had one outstanding document immediately mailed to the person who helped me. She said that it would be done. When I asked if I could not have written proof that the change would be made (i.e. that I would no longer be charged by R1890-odd contract fee effective 1 October 2018, and would move to prepaid) she laughed me off dismissively and reassured me "Don't worry, it will be done." When I picked up my phone on 1 October, however, I saw that I was still able to make calls etc. although I had not bought prepaid credit. I immediately called the store and, after a lot of backwards and forwards, was told by the person handling the query that she had simply forgotten to process the request. While I commended her honesty, I said to her that she needed to understand that her forgetfulness was costing me nearly R2000 - I had in the interim app**** for a R1000p/m contract with MTN, and was planning to use prepaid until this came into effect. I was, understandably, angry. Even angrier and filled with more disbelief when I called MTN to discover that they had, also with no reasonable explanation except neglect, forgotten to activate my new contract! So here I was stuck with a R1000 more expensive contract than I had planned for. While I should probably have made a bigger fuss at the time at Vodacom, I felt sorry for my assistant, and was so shocked by both MTN and Vodacom's absolute uselessness so I told her that - even though I was out of pocket (I would have managed my spend on prepaid to be much less than the R2000 contract) - we could just leave it. She assured me that she would rectify her mistake but that as contract changes are only made monthly, she would process the contract termination and move to prepaid effective 1 Nov. Imagine my utter disbelief when I turned on my phone at 05h30 on 1 November and was still on contract! I wrote her an email immediately to ask what on earth was going on. She never responded to my mail. I call her, and she promised to call me back. She never called me back. I called back the next day, and she told me that the central Vodacom office had said that they had not processed the cancellation because they had not received the required authorisation as an attachment from her. She was adamant that she had sent it, and was quite defensive when I asked her how on earth this could happen, and told her that - as I had written in my mail - I was now R3000 poorer than I would have been if she (and potentially the central contracting office, depending on whether or not she had sent the attachment - I asked her to forward me the mail that she had sent but had no luck getting this from her) had not forgotten in month one, and failed to follow up and ensure that the process had been completed in month 2. If it were me, I would have made DOUBLY sure that everything was done, bearing in mind month 1's mess-up. So now I sit with two contracts in November, i.e. R2000 out of pocket for November, and having been on a more expensive contract than planned for October, to the amount of R1000, so R3000 out of pocket. I am absolutely flabbergasted. When I have asked her what her suggestions are on my recourse, she says there's nothing that she can do, that she can only cancel it effective 1 Dec. Are you kidding me, Vodacom???