How do I charge to my redeemed gift card on iTunes rather than my credit card?
My friend got me a $10 iTunes gift card, so I entered it on my iTunes account and it says it redeemed, but nothing is being charged to it, it is all being charged to my credit card. I have tried to change that by doing anything I can on my accout settings, but there is nothing there that I can find that helps. So how can I change my payment method to charging the redeemed gift card?
$500 American Express Gift Card Free Priority Shipping

It always charges purchases to the store balance first, if there is one. Either it didn’t actually redeem or you had a previous purchase with an insufficient store balance and your credit card couldn’t be billed for some reason, perhaps because of an expiration date or even a change of address. Get help from iTunes.