Clearing the phone memory on your device can help when you are running low on memory, purchase a used phone, or simply want to restart at default settings. A phone memory clear will restore the original factory settings and may erase all contacts, messages and downloaded content (including ringtones, images, programs and contacts) stored in the internal memory. Back up any information that you do not want to lose permanently.
Select the "Menu" option from the main screen on the phone.
Scroll to and select "Settings."
Scroll to and select "Phone settings."
Scroll to and select the "Security" option.
Select the option to "Reset" or "Wipe."
Select the memory options that you want to clear from the device, such as "All," "Sound settings," "Display settings" or "Phone settings."
Select the "Reset" option to begin the clearing process.
Click "Yes" when a confirmation message appears.
Type in your security password. If you have not set up a password, the default is typically 1234 or 0000 (four zeros).
Select "OK" to finalise the process.
Steps may vary slightly based on your manufacturer (such as Samsung or Nokia). Please refer to your specific manufacturer's site for details.