Vodacom in my opinion the worst cellphone network in terms of customer care

As usual bad service and they even get away with unathorized upgrades. cancelled my contract last year with vodacom. Somebody upgraded my contract without my knowledge or permission. I contacted Vodacom and customer care advised me to get an avidavid and my id to state this. They cant prove my upgrade but even if I did everything that they asked I still pay for something I did not asked or signed. Ho is that fair or possible.