On the phone press 'Menu' then select 'Basic'. 

Use the arrow key to scroll down to 'Bluetooth' and press 'OK'

Make sure Bluetooth is 'ON'

Make sure your pair your Bluetooth device, such as a headset with the phone - your device should be listed - select the device and make sure this is set to 'ON'

Press the 'Back' key to exit out of the menu options.