HT201209 How to use an Itunes Gift Card

We entered our Itunes gift card code and it is showing that we have a $50 balance.  However, when we try to purchase music, the charge is still going to my credit card.  How do we resolve this problem?

You can't. When you redeem a gift card it's redeemed onto the account (not the device) that you redeemed it onto, so it will be available wherever you use that account - you can't redeem a card twice, nor copy (or gift) any of its amount to another account.