Bought an I-Tunes card for my niece in Sainsburys at Christmas.She only got around to using it last weeek and discovered that it needed to be swiped by the shop before it could be used .Brought it back to Sainsbury but they would not swipe it as I did not have the receipt.Is there anything I can do??Surely they should have swiped it when I bought it but I didn't know this ......