How to get a refund for Apple Gift Cards?

I received an E mail from a friend asking me to buy some Gift cards on her behalf. This turned out to be a scam as her computer had been hacked. Before I knew this I bought 3 £100 gift cards from a local supermarket. As soon as I realised I had been scammed, I called Apple to ask that the cards be rendered unusable...the guy I spoke to said this had been done but I would have to go to the store where I bought the cards to get a refund. Is there a way to get a refund direct from Apple? Alternatively will apple provide me with documentation which I can take to the store for a refund?

[Re-Titled by Moderator]