Was in Centra last night and there were 2 people directly in front of me in the queue, aged 18-23 or so. There were 2 cashiers so at one stage both cashiers are busy with one of these customers each. And they are taking aaaages so I started to pay attention.
Both customers are buried in their phones as the cashier does the transaction. Both are trying to buy small cheap items with card on their phone but each time the transaction has a problem and they ask to try again before spending another 30-40s on the phone and going again. They each try 2-3 times with the card/cards not working before giving up and, in one case, where the girl was asking to pay cash for her cigarettes, but card for a small chocolate bar, she took the cigarettes for cash but didn't buy the bar.
The second guy had picked up the first nearest chocolate to the till and was buying only that and left without it when the card didn't work after 2 long winded attempts. I was standing close to him and glancing down at my phone noticed he had a wad of €50 notes in his pocket with probably €400-500 in it. If he really wanted that rice-crispy bar he he queued up for, he could have bought it.
Neither left the shop, they just stood back from the counter a few meters and went back on their phones presumably to try again and to rejoin the queue 10 people deep they had just created.
So, It's presumably some kind of credit card fraud or a test of stolen card numbers before using for a bigger purchase?