I received an iTunes Gift Card in the amt of $15.00. I redeemed the card on your web site and was informed that my acct now has a $15.00 credit. When I attempt to purchase songs I am refused saying I have an invalid code.

I received an iTunes Gift Card as a Christmas Present in the amt of #15.00. I validated it using the code on the card on your web site and was informed I now have a $15.00 credit. I then attempt to buy music downloads and when I attempt to pay using the code on the gift card I am told it is an invalid code. Several times I have tried getting the same results. Since it was a gift I do not have a receipt or know where the card was purchased. This is very discouraging. Help please....