dh recently had a jetstar flight cancelled a few hours before the flight, he was the photographer for a wedding the next morning so he HAD to be there on time. Jetstar offered a flight the next day and when we said that wasn't an option, they offered a refund. I quickly booked him a new (more expensive) flight with Qantas and sent him on his way. You wouldn't believe it, the flight missed the Sydney curfew by 1 minute, 1 minute!!! They were coming in to land, then they were back up again, and on their way back to Melbourne, he got home in the early hours of the morning, and rebooked on a stupidly early flight as that was the only way he was going to get there. Crazy. He should have just stayed at the airport!

Sorry, that was a bit long! So, yes it seems that they can change it, but you should be able to get a refund at least, it doesn't help with the inconvenient times though!

Hope you can work it out and you have a fabulous time