I just had a similar change but with the added impact that the A320 service doesn't have Business Premier, only Economy. I'm booked SYD-AKL-LAX and the SYD-AKL looks like the last flight of the day. I don't particularly want to move to an earlier flight. Would it be worth asking if I could move to a set of flights the following day? The midday flight appears to be the only service not on the A320.