In order to hard reset a Siemens U10, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Siemens U10 device will be brought back to the default configuration of a brand new device.
1. Heyoo. Start by turning on the phone with the Power button.
2. Type in your phone's secret code *#9999#.
3. Lay back and wait for the phone to reset and restart. Done!