Keep bumping us to worse cheaper times without compensation

I have booked 6 different flights over December/January recently from Melbourne to Newcastle and Cairns, all were booked for around 11am flights as we have a baby and a toddler and can get them to sleep around that time. We paid extra to get these times over the cheaper 6am flight so we didn't have to wake them at 4am.

Jetstar has moved 3 of the flights so far to the crappy 6am slot without any compensation to the premium we paid over the cheaper flight. Not only that but all the afternoon flights have now tripled in price!

Australia-Melbourne - Tullamarine