In order to hard reset a Ericsson GS 18, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Ericsson GS 18 device will be brought back to the default configuration of a brand new device.
1. Power up the device.
2. Scroll to Settings, enter by pressing Yes and then select Master Reset.
3. Enter, if asked to, phone's lock code (default code is 0000).
4. Confirm by pressing Yes. Done.