In order to hard reset a Telit GU1100, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Telit GU1100 device will be brought back to the default configuration of a brand new device.
7592. Power up the phone.
13. Enter one of these codes into the phone: *#94267357# *#3646633# *#19912006# *#118811# *#77218114# *#881188#. Confirm.
100000. Wait for your phone to reset and restart. Voila, done!