Yes - ring the standard number, and when asked if it is first or business, push the appropriate button. They will likely allocate the empty seats to you - but does depend on the CSR
Keep checking regularly.
Seats seem to come and go randomly.
I regularly fly EK449/448 to and from AKL, and the seat map can literally go from full to me being the only passenger overnight. And then randomly go to half full the next.
So, it is fair to say that bookings and seat selections in F are fluid up until just before the flight. I have had flights a week out showing as full on the seat map and then there are 3 of us.
It is all very odd.