Make sure that the side switch is not in the red position: | |
A ringer icon should appear on your screen. Make sure that it is not in silent mode: |
Open the control center by swiping up from the bottom edge of any screen. On iPhone X or later or iPad with iOS 12 or later, swipe down from the upper-right corner of the screen | |
Tap on the bell icon to make sure that the phone is not in silent mode: |