How do I change my payment info to another credit card
How do I update my payment info to another credit card on iTunes ,ibooks
On your computer's iTunes you should be able to edit your payment info by going into the Store > View Account menu option and logging into your account, and on your account's details page there should be a payment link. If you are doing it on an iOS device (iPad, iPhone or iPod Touch) then you could try tapping on your id in Settings > Store (Settings > iTunes & App Store on iOS 6+) and selecting 'View Apple ID' on the popup - that should also give you a payments link on your account's page.