Do a dummy 'flex' booking for the same JQ flight and go to seat selection. You can then see what seats are available. Also do a dummy 'saver' booking and compare to see which seats may be blocked. (Of course, do not complete these dummy bookings.)
After that it's time to call JQ armed with your flight details. At which time you can:
- Confirm the Booking
- Establish you have the correct JQ reference
- Request seating
Goo Luck ...