Press Applications. Go to Admin settings > Reset settings > Reset device.
Resets any user and network setup changes that you have made, but that the phone has not written to its Flash memory, to previously saved settings, then restarts the phone.
Reset settings
To reset settings, press Applications and choose Administrator Settings > Reset Settings > Network.
Resets user and network setup settings to their default values, and restarts the phone.
To reset the CTL file, press Applications and choose Administrator Settings > Reset Settings > Security.
Resets the CTL file.
User Guide
For information on how to operate your Cisco device not referenced here, please refer to the user guide.