Reconnect the headset
If you disconnect the headset from your mobile device, you can reconnect
the headset to the device without switching the headset off and back on.
Press and hold the multifunction key for about 2 seconds, or make the
connection in the Bluetooth menu of your device.
You may be able to set your mobile device so that the headset connects to
it automatically. To activate this feature in a Nokia device, change the
paired device settings in the Bluetooth menu.