Kyocera 2100 Series - Manual (Page 12)

Resetting the phone
If the screen seems frozen and the keypad does not respond to keypresses,
reset the phone by completing the following steps (see see page 3 for
detailed instructions):
1. Remove the battery door.
2. Remove and replace the battery.
If the problem persists, return the phone to the dealer for service.
Qualified service
See “Frequently Asked Questions” on page 93 if you are experiencing
problems with your phone.
If you have additional questions, contact your service provider for technical
support. If the problem persists, return the phone with all accessories and
packaging to the dealer for qualified service.