It would be interesting to persue whether the fee is payable if the passengers don't get out at Rottnest.
I did get a win with Avdata and they don't try to mess with me now.
It's Airservices who are currently causing a lot of wasted time chasing credits for double charging for landings and charging for days the aircraft never flew.
Last Airservices bill approx. 10% of the charges were false.