Need to change credit card?
Need to change credit card
iPad, iOS 7.1
On your iPad try tapping on your id in Settings > iTunes & App Store and select 'View Apple ID' on the popup - that should give you a payments link on your account's page. If doing it 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 also be a payment link.
Changing payment info : http://support.apple.com/kb/HT1918