Instruction I:
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!
Instruction II:
1. Turn on the phone's display.
2. Next, press'n'hold the Power and Volume Down buttons for, say, ten seconds.
3. Your phone will now vibrate and reboot, meaning that the soft reset process is complete.