If anyone is paying by EFTPOS/credit card in your shop make sure that you get a photo of the customer. It may help.
What has happened to one of my clients is that last month as they were doing a credit transaction from a potential customer. The shopping assistant noticed that was doing the sale it looked suspicious, the amount was very high, the person had just grabbed a few items without thinking, was acting funny and seemed to be moving to try to avoid the cameras. So he told the person to wait for a second as he needs authorisation from the bank, which he did not need but it just did not look right. The person immediately ran out of the store leaving the card behind. The card turned out to be stolen.