1. iMessage is built into iOS versions 5 and later, and allows you to send unlimited text, photos, videos, locations, and contacts using Wi-Fi or cellular data from your iPhone or iPad.
   Note: iMessages are billed as data usage when sent over a cellular data connection. Messages will be billed as text messages when sent to other device types, or to iOS devices using an earlier version of iOS. You need a valid phone number or Apple ID to use iMessage on iPhone.
   
2. From the Home screen, tap Settings.
   
3. Tap Messages.
   
4. Tap the iMessage switch to turn on or off.