Shell - Bedworth Park Unclaimed

when I saw this add on the display board on the corner, I went in to refuel with diesel. when I got to the pump, the price display was R12.60. I asked the attendant by the board says R12.23. I asked where the manager was and the answer was that she went home again. How many people were misled by this add and they did not even pick it up. I insist that the difference between the 2 prices being given back to me for that amount that I spend when I filled my vehicle. Or I must sent ti to Carte Blanche.