To swap a Zigbee enabled switch to Bluetooth, press the switch 4 times and hold on the 4th press for 20+ seconds.
When holding the button in at the 10 second mark a slow flashing red led should be visible, releasing at this point would be a factory reset. Continue to hold until the red led starts flashing rapidly at the 20 second mark and then release.
This method of changing the mode of the mechanism will work Zigbee to Bluetooth and also Bluetooth to Zigbee.