1. Open your iPhone's. Settings. ...
  2. Scroll down and tap. Do Not Disturb. ...
  3. Tap the white "Do Not Disturb" switch. . ...
  4. Tap Allow Calls From. This option is near the bottom of the screen.
  5. Tap All Contacts. Doing so will select your entire contacts list as the exception to Do Not Disturb.

I hope this helps.