Go to messages then click the menu button and go to settings go down to the bottom and under "Notification Settings" and click the tick box for "vibrate" that should work.
Menu>Tones>Settings... scroll down to `Vibrating Alert`.
For silent, just drag down the top bar and click on the ringer icon, this puts your phone on silent and automatically activates vibrate. Revert the same way.
Every question has an answer?
http://technoanswers.blogspot.com/2012/01/every-question-has-answer.html
To make it normal ringer function.select another option,so it will stop vibrating.
In some cases the problem is setting reset.In that case the cell has to be reset or set to factory default settings.
If you need that our Techno Experts should provide you more details.
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Thanks.