You can change your Qantas flight (date, time or destination) via the “Manage Booking” section. Whether changes are free or cost anything depends on your fare type (flexible vs restricted). More flexible tickets generally have lower fees or none. If you change close to the departure time, you may need to pay a change fee as well as any difference in fare if the new flight costs ... https://getmesky.com/qantas-flight-change-made-easy/