Enable or disable Group Messaging on iOS devices
Turn Group Messaging on or off on your iPad, iPad mini, iPod Touch or iPhone
Here's how you can enable or disable Group Messaging on your iOS device.
1. Open the Settings app.
2. Tap on Messages.
3. Tap the Group Messaging toggle to On or Off.
For more, see the original article at the link below.
iPhone 5 Tips and Tricks | Apple