Extra billed and no help from support division

On 20 Nov 2015 I used Uber for the first time for a trip from Westville to Shongweni, then back again. Bill came through to my phone and email. 20/11/ 2015 R109.98 and 20/11/2015 R190.04, plus a cancellation of R17.50 (which I never cancelled). Then on 22/11/2015 my credit card was charged AS WELL with amount of R731.91.I have tried Uber support and all they tell me is I must find out who else I know that would have access to using my credit card. I have explained that no-one else has, and asked for the invoice for R731.91 to no avail. I did not use Uber on 22/11/2015 and if I do not get an explanation and refund for this I will be taking it further. Perhaps the only person who had access for the next ride would be one of the drivers that took me on the Uber on 20 November. I will be reporting this further if no explanation is forthcoming from uber support.