Duplicated Credit Card Transaction

On 2 May 2015 I went to purchase some food stuff at Woolworths Plattekloof at a cost of R748. I fortunately get SMS notifications when I purchase with my Credit Card. My purchase SMS came through at 12h45. When I got home resting and recuperating from having the Flu I got another SMS notification at 15h56 to show another transaction for the same amount gone through my card. <br> I decided to check my online account and found that there were two deductions from my card.<br> When I contacted the number given on the SMS notifications, they tried there best to help but I ended up having to go back to the Store this morning only to be told that they don't know how or why its happened but they have refunded the error.<br> Not good enough for my liking. I want to know how a duplicate transaction took place and did it happen to anyone else.<br> A reversal of an error is not an explanation as to how it happened in the first place while I wasn't even in the store.<br> Im annoyed and frustrated. <br> Thanks Woolworths for trying to cheat me out of my hard earned cash. Your one saving grace is that the person that helped me over the phone was FANTASTIC and a very valuable employee.