Q: I've added a gift card to my account to purchase music but it's trying to charge my credit card instead of the gift card. How do I change this?

Hello Bettymg36,

When you make a purchase in any of the digital stores that Apple has, it will take fund from the following order: Free song credits are redeemed first, gift certificate, prepaid card, and allowance credits are used next, then it is gift certificate, prepaid card, or allowance credit which finally foes through your credit card. If you are billed through your credit card, report the issue with the second article below. 

How iTunes Store purchases are billed

http://support.apple.com/kb/HT5582

Report a problem with an item you bought from the iTunes Store, App Store, Mac App Store, or iBooks Store

http://support.apple.com/kb/HT1933

Regards,

-Norm G.