Change text (SMS), picture (MMS), emergency, and AMBER alert settings.
In this tutorial, you will learn how to:
• Access Messages app Settings
• Adjust Notifications
Messages settings allow you to control image size, message history, and more.
1. From the Home screen, select the
Settings app.
2. Scroll to Apps >
Messages > adjust Messages settings as desired.
Note: Available options vary when iMessage is turned off. 
1. From the Settings screen, select Notifications then scroll to and select Messages.
2. Edit your Messages notification settings as desired.
Note: Learn more from the Apple website: https://www.apple.com/ios/messages/. 