After you change your payment information, the i Tunes Store will place a temporary authorization hold on your credit card to verify your updated account information.
If you have any issues updating your payment method, visit Apple’s support site for further assistance.
Before you change your email address, it is important that you sign out of every other Apple device and service that uses your current Apple ID.
If your current Apple ID uses an email address that ends in @me.com, @or @mac.com, you might not be able to change your email address and the Change Email Address field will not be visible.
To change the credit card you use for i Tunes and App Store purchases, find the Payment Type row and click the Edit link on that row to open a new screen where you can enter new credit card information. Similarly, change the billing address by clicking Edit in the Billing Address section.