Text message from Jetstar saying our flight has been cancelled

I have receieved a text message saying out flight has been cancelled the day before we are due to flight out. Getting a message via text is one thing it also took me 65min to get through to them via phone. No explaination of why was the flight cancelled they simply told me 'we can transferr you to avalon airport' everyone knows avalon airport is futher away from cbd and there is a cost different between avalon airport and tullamarine. Their customer service has informed me their flight are full in the morning therefore i either take avalon transferr or get refund, if i did take up the transferr they will not payou the difference between the two airport ticket price or any compensation. After 20min arguing over the phone they decided 'oh we do have a flight to fly you out at 11am' our orginal flight is at 7am (our frd's wedding is on that day).
Leaving us no choice we have to take up the transfer offer to avalon.
After calling both sydney and melbourne airport i have been informed our orginal flight will be flying out as normal!???!!