In order to hard reset a Sagem my400V, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Sagem my400V device will be brought back to the default configuration of a brand new device.
1. Press-hold the Power button to turn on the phone.
2. Open Menu and go to Settings, Backup & Reset and Factory Data Reset.
3. Continue to Reset Phone and Erase Everything. Done! Phone should reset and restart.