I'm not cabin crew, but I do work for QF. One way to stop these people is to have a look in the policy and procedures manual and quote it back at them (a polite way to tell them to F**K Off).
Most of the managers I have come accross at QF have no idea what is in this manual and because of this you have them on the back foot.
I have seen it a number of times when they have gone to sack someone but failed because they did not follow the company procedure set down. I have seen this happen with department managers and even HR people. They all seem to have no idea what is in it.
Another reason to look in it, is that you can normally find some company rule somewhere that will help you cover your arse if needed.