Hi

Yesterday, as part of a longer open-jaw itinerary, I booked MNL-HKG-SYD in discount business class (fare bucket I), with 3 pax on the itinerary. Current flights are (on 8th Jan 2024): MNL 0800 - 1030 HKG CX912 connecting to HKG 1920 - 0725 SYD CX111, so we have an 8'50" stopover in HK, which was intentional.

However, having now done some more thinking about the itinerary and to allow more contingency in case of domestic flight issues in the Philippines, I wanted to change to the 12.35pm departure out of MNL (CX930), connecting to the same SYD flight. I'm within the 24hr period within which I can make free changes.

CX930 was an option I could book at the same fare basis yesterday when I originally made the booking, and looking at CX930 on its own, Expertflyer shows I6. However there's no more I class available on the HKG-SYD sector so the agent is saying they can't make the change at the same fare basis. Of course we already have 3x I class seats on the HKG-SYD sector we want, but the system seems to be looking for 3 additional ones. I know that in theory I could cancel the booking with no penalty and hope that all the I class inventory reappears, but I really don't want to take that gamble, as I was lucky to find the fare I did at that time of year (the outbound sector is BNE-HKG-NRT just before Christmas) so I'd rather keep the existing booking than take that risk.

Is there any way around this? The agent didn't inspire me with confidence so I'm not sure whether there's a solution she doesn't know how to do, or if I'm just out of luck here. Would really appreciate any advice

I doubt that there is much you can do.

Not even sure you can avail from the 24h free cancellation .
You need to be a CX member at time you made the booking and that seems to apply to free cancellation not changes.
But maybe Australia has different rules.

You get the free cancellation as long as you enter your CX membership number to the booking before you hit the cancel button