I booked lowest business reward, then made a change to the date so i paid the 100$ change fee, but forgot to choose flex for the new booking as well. tried to call in to upgrade from lowest to flex incase i need to make any changes, but they said without availability they're not able to do it even to upgrade to flex....
So not sure if i should even try now or just leave it as lowest business.

Thought of cancelling & rebooking since it's still within 24 hour of the change so free cancellation but didn’t want to lose my spot on SG business class. Not sure if the spot will go back to inventory?