1. Hold down the Power button in order for the menu to show on screen.
2. Choose the Power off option.
3. After a couple of seconds, hold down the Power button again. Your phone will turn back on. Voila.
1. First of all, take off the phone's back cover and remove the battery.
2. Wait a few seconds and reassemble the phone. Lastly, press the Power button to turn it on. Done!