If you’re in a place where your phone sounds may disturb others, you can quickly silence your phone from the Home screen.
From the Home screen, press and hold the Power/Lock Key (on the back of the phone), then tap the Silent mode icon .
Only one mode can be selected at a time. The currently activated mode (Silent , Vibration , or Sounds ) is underlined in blue. Tap any of the sounds mode icons to switch to that mode.
OR
Press the Volume Down Key on the back of the phone (when the screen is not in time-out) until vibration is set, then press it again to turn all sounds off.
OR
Open the Notifications panel and tap the Sound icon until is displayed.