iTunes Store

I changed my email address at iTunes, but my iPhones still use the old!

How do I change it in the phone?

iTunes store
From one of your home screens, find and tab on "Settings"
Scroll down and tab "Store"
Tap on the "Sign Out" button
Then, tab on "Sign In"
Supply your new Apple ID (email address), and your password
You are now signed in using your new Apple ID