When the iPhone crashes, locks up in a way that prevents the iPhone from responding to being turned off, or just isn't working as it should (you'd be surprised at how many problems can be solved by a simple reset) you need to reset the iPhone. Here's how:
- Reset the iPhone by holding the sleep/wake button at the top right of the device and the home button at the bottom center of the face at the same time.
- Hold them both until you see the screen go black. In some cases, you may need to keep holding them even after the red power off slider appears. If it does, just keep holding it.
- Wait until the white Apple logo appears.
- When this happens, you can let go - the iPhone is rebooting.