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You will have to perform a factory reset of the device. Resetting will DELETE ALL DATA and reset the phone back to the state before you turned on the phone for the first time. SD card will not be affected.To perform factory reset please follow those steps:
1. Power the device off.
2. Press and hold the Volume Up key and the Power key simultaneously to power on the device.
3. Release the Volume Up key and the Power key when the Samsung logo displays on the screen.
4. Use the Volume keys to select Recovery Console then press the Power key.
5. From the Recovery Console screen, use the Volume keys to select Wipe Data/Factory Reset then press the Power key.
6. Use the Volume keys to select Yes then press the Power key.
7. Once the Wipe Data / Factory Reset has completed, use the Volume keys to select Reboot System Now then press the Power key.
8. After a Wipe Data / Factory Reset has been performed, the device will need to go back through the activation and setup process.
Please check the picture below:Picture - click here
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