In order to hard reset a BenQ-Siemens SF71, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
BenQ-Siemens SF71 device will be brought back to the default configuration of a brand new device.
1. Turn your phone on.
2. Type in this sequence - *#9999#
3. Your phone will now restart.