From the T & Cs (emphasis added):
14.7.6 Subject to this clause 14.7, the following changes are permitted to a Classic Flight Reward flight before departure
of that flight, provided the booking contains one or more Flight Segments that are not within Australia, and the Flight Segment(s) being changed do not include a partner airline that requires a ticket to be reissued for the change. Any such change will incur a Change Fee (see the
Fee Schedule) per passenger:
(a) change to flight number; and
(b) change to date of travel.
So, in answer to your question (and assuming you have an international segment which, of course, is what this thread is all about), my understanding is:
- After you have departed on your first leg, you can change the date and or time of a flight (changing the time will usually result in a change of flight number);
- After you have departed on your first leg, you cannot change the flight route, or class of travel, or carrier...