Q: i phone 4s

Hey Punitverma! 

I definitely understand not wanting the flashlight on your iPhone to be on all of the time since that isn't expected behavior.  No worries though, there are some things to do that should take care of it.  If you've tried some of these steps already then it's fine to just skip to the next one.  

The first thing that we want to do is make sure that you have a current backup of your iPhone to make sure that all information is safe.  For those steps you can check out this article here: How to back up your iPhone, iPad, and iPod touch

Once that's complete, we'd want to try by restarting your iPhone.  This article can show you how to do that: Restart your iPhone, iPad, or iPod touch

If the flashlight is still on after that, try to take a picture with your iPhone where you have the flash turned on.  After that, quit out of the Camera completely by following these steps: Force an app to close on your iPhone, iPad, or iPod touch

After those steps are done, if the flashlight is still on and won't turn off, we'll need to Reset All Settings.  Doing this step won't cause you to lose any user data on the iPhone but it'll reset things like your icon layouts, Wi-Fi passwords, and VPN settings. To be able to do this reset, go to Settings > General > Reset > Reset All Settings.  

The last step that to do if nothing has solved it so far is to restore the iPhone to factory settings to test it out.  To do that, follow these steps: Use iTunes on your Mac or PC to restore your iPhone, iPad, or iPod to factory settings

Cheers!