LG -P713 User Manual page 366

Important notice
While making/receiving calls or sending/receiving data, avoid holding the lower part of
the phone where the antenna is located. Doing so may affect call quality.
8. When the screen freezes
If the screen freezes or the phone does not respond when you try to operate it:
Remove the battery, reinsert it, then turn the phone on.
OR
Press and hold the Power/Lock key for 10 seconds to turn it off.
If it still does not work, please contact the service centre.
18