In order to hard reset a AEG QSX400, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
AEG QSX400 device will be brought back to the default configuration of a brand new device.
1. Turn the phone on by press-holding the Power button.
2. Starting from the Home Screen, open Menu and Settings.
3. Now tap Reset and Master Reset.
4. Lastly, select Yes and type in the safety code 1234.
5. Voila, done.