Here's how to Factory Reset your VoIP Phone:

Snom 3xx/7xx Series

Since firmware version 8.7.3.7 on the Snom 3xx Series it is possible to reset the phone using the key pad by pressing the following key sequence:

* Volume Up * Volume Down #

Default administrator password is "0000".

Reset to factory defaults via Phone Interface:

Snom 300 - Press "Navigation" down to enter the "Settings" menu, scroll down to "Configuration", press "Confirm" button, scroll down to "Reset", press "Confirm" button, press button under "Reset" on display, enter the administrator password then press "Confirm" button.
Snom 320 - Press "Settings" button to enter the "Settings" menu, scroll down to "Configuration", press "Confirm" button, scroll down to "Reset", press "Confirm" button, press button under "Reset" on display, enter the administrator password then press "Confirm" button.
Snom 360 - Press "Settings" button to enter the "Settings" menu, press 10 for "Maintenance" menu, press 5 for "Reset Values", press "Confirm" button, enter the administrator password then press "Confirm" button.
Snom 370 - Press "Settings" button to enter the "Settings" menu, press 10 for "Maintenance" menu, press 5 for "Reset Values", press "Confirm" button, enter the administrator password then press "Confirm" button.
Snom 710 - Press button under "Settin" on display, press 5 for "Maintenance" menu, press 4 for "Reset Values", enter the administrator password then press "Confirm" button.

The phone reboots automatically.

Reset to factory defaults via Web User Interface:

Obtain your phone's IP address and currently used firmware version by pressing the Help button on your Snom 3xx.
Open any web browser and choose the URL corresponding to your current firmware version:
- Firmware versions lower than 3.X - http://1.2.3.4/set_base_en.htm?reset=Reset
- Firmware versions between 3.X and 6.X - http://1.2.3.4/advanced.htm?reset=Reset
- Firmware versions from 7.X onwards - http://1.2.3.4/advanced_network.htm?reset=Reset
Copy the appropriate URL into the address line of your web browser and then change "1.2.3.4" to your phone's actual IP address.

The phone reboots automatically.