Given the ferocity with which I have seen many self-important people on planes persist in using their phones when they have been requested to turn them off, I have little doubt that cabin crew have been told by these people that continuing/making their call is vital for any number of fanciful, yet seemingly urgent reasons (e.g., left the baby strapped in his car seat in the car park, forgot to turn off the gas on the oven, etc.). How can you expect the crew to separate the liars from the truthtellers? And how do you give guidance as to exactly how urgent the call need must be? There will always be a new reason offered. There is no reason for this crew to be chided for enforcing standard regulations.