Vibrate on iPhone 4S not working -HELP-?

Go to
- Settings
Click on
- Sounds

( Make sure the Vibrate On Silent is on, & the volume bar is all the way up. )
I it still doesnt vibrate, click on
- Ringtone
And make sure it doesnt say "none" next to vibration. If it does, click on
- Vibration
& you pick one of the vibration patterns that are available.. You can even make your isn vibration pattern which is incredibly cool!
If it still doesnt work, then maybe try taking it to your carrier & see if they can diagnose the problem?? Hope i helped!

go to the service center ..or check if you have accidentally switched off the the vibration