In order to hard reset a Nokia Asha 308, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Nokia Asha 308 device will be brought back to the default configuration of a brand new device.
1. Power up the phone.
2. Now open the Dialer and press-hold the 3 + * buttons until the Nokia logo pops on-screen.
3. Press Left Softkey to confirm the operation.
4. The phone will now reset and restart.