How to Fully Flush Your Phone
Just about every phone has the option of flushing all the user information and data out of the device. This option is usually called a master reset, although some devices call it a master clear or hard reset. Either way, make sure the data you want to keep is backed up before you begin, because this operation sets the phone back to its original factory settings.
Click the "Menu" button on the phone, or tap the "Menu" icon for phones that have touchscreens.
Open the "Settings" option. The master reset option is almost always located under one of the menus under Settings. Look for an option called "Privacy" or "Security."
Click the "Menu" or "Options" button and look for a command that says something about resetting or wiping the phone.
Check the phone's user manual if you can't find the setting. Most user manuals indicate how to reset the phone and wipe the data.
Browse to the manufacturer's website and search for support documents on your model of phone if you can't find the instructions in the manual. Also contact your cellular carrier's tech support.