Duplicate Transactions Online Card Purchases.

What's the point of having a bank card if you're afraid to use it because your transactions keep getting duplicated??? Twice now I've been promised feedback from the card division, and still nothing. Thus far all I've received is a reversal form. What I've been asking for is an explanation as to how this can be allowed to happen with only a single OTP, and a confirmation that the issue has been rectified so this won't be allowed to occur again. Nobody seems to be able to comprehend my issue. I'm at a loss for words right now.