The article below will help you review your iTunes Store account and update billing information:
Changing your account information using an iOS device:
- Tap Settings on the Home screen.
- Tap iTunes & App Stores.
- Tap on your Apple ID. (If you are not signed in, enter your Apple ID and password, and tap Sign In.)
- Tap View Apple ID.
- Enter your Apple ID password.
To update your email address, follow these instructions:
- In the Edit section, tap the Apple ID field.
- Tap the Apple ID field.
- Enter the email address that you would like to be your Apple ID.
- Tap the Done button.
To update your name, billing address, or payment information, follow these instructions:
- In the Edit section, tap Payment Information.
- Update the information that you want to change.
- Tap the Done button when finished.
I hope this information helps ...