Amazon giftcards

So... I bought an Amazon gift card and used it on my account, but now it's asking me for my credit card info when I'm trying to pay with it.
Is there any way to get around that?...

Confirm that you redeemed your code first.
If that's not the problem then just change your purchasing options. It'll list all the payment options you can use if you go to your settings and pick a different one.