If your iPhone does not vibrate when you move the Ring/Quiet switch back and forth, it is possible that the vibrating is turned off or that your device is set to either ring or silent mode. In order for your iPhone to vibrate for incoming calls or text messages, you must enable either the Vibrate on Ring or Vibrate on Silent option. Here's how to do it:

1. From the Home screen, choose Settings.
2. Sounds and haptics may be activated by tapping on the screen.
3. Next to Vibrate on Ring or Vibrate on Silent, tap the switch. If the switch is green and in the correct position, the choice is switched on or enabled, and you're ready to go.