Perform a soft, factory, and alternate master reset of the device.
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INSTRUCTIONS & INFO
There are multiple ways to reset your device if you are experiencing issues. The first step is to power cycle your device. Press and hold the END button to Power off. To turn the device back on, press and hold the Power button until the screen lights up. Note: If you are unable to turn your device off, remove and re-insert the battery.
If a restart does not resolve your issue, you may need to perform a Factory data reset (Master Clear). This will erase all data on your device and restore it to factory settings. To ‘Factory data reset’ your device, select Menu > Settings > Phone Settings > Reset Settings > Master Clear > Phone > Yes. Note: A Factory data reset will revert the device back to factory settings. It will permanently erase all personal data, preferences, settings and content such as pictures, ringtones and apps that are saved to the device. It is recommended that you save (backup) important data before proceeding.
If unable to perform the standard ‘Factory data reset’ using the above steps, try the Alternate method by entering 3845#*470# on the dial pad. Then select Factory Reset.