How to Use a Different iTunes Account for an iPhone
To buy and download media from the iTunes Store, you need an Apple ID. Apple IDs are unique, but you may have more than one. If you want to use a different account for the iTunes Store on your iPhone, you will have to sign in with a different account user name and password. You can sign in to a different iTunes account directly from your iPhone.
Press the "Home" button, and unlock the iPhone by sliding your finger across the "Unlock" bar on the screen.
Tap the "Settings" icon. This will open the Settings menu page.
Scroll down the page. Locate the "Store" tab and tap it once to open it.
Tap "Sign Out" if another account is currently signed in.
Tap "Sign In." A sign in prompt will appear, asking for your account information. Type your user name and password in the appropriate fields, then click "OK."
Tips & Warnings
- If you want to create a new iTunes Store account, select "Create New Account" from the store page.