tinpis, I believe the origin of your tale was somewhere near Adeliade soon after Australian got their shiny new 737-300s. As has been discussed at length here on other threads, the learning curve from the -9 to the 733 was steep to the point of being past vertical, particularly since Australian management had forgotten to allow for line training in the very tight plan they'd drawn up to introduce the new aeroplane.
Someone will doubtlesly correct me if I've got it wrong, but I think line training was four sectors, and there'd be few newcomers to the 733 from the -9 who'd consider that adequate.
Scene: Australian 73 is asked to descend by ATC. The 73 pilot responds. Pause. ATC asks 73 to call leaving. 73 acknowledges. Pause. ATC: "(c/s), have you left 310?" "Standby." Long pause. Second voice (the AN 733 also on frequency): "Press Level Change." "(c/s) left flight level 310."