There is no fee to change but you usuall

Posted by sherbert on Wednesday, 18. July 2012 at 16:11 Bali Time:

In Reply to: changing ticket posted by bluey on Wednesday, 18. July 2012 at 15:09 Bali Time:

end up paying a difference in price. All you need to do is call up your booking on the Jetstar website and you will see a change flight option.