The best solution I have seen to the problem of passengers who know best and use their mobile phones when they are not permitted to was demonstrated by a BA shorthaul crew after landing at Heathrow.
1) During taxi to the gate, a very important businessman turns his mobile phone on and calls his wife to say he will be late home because of our awfully long delay.
2) His unnecessarily loud conversation is overheard by cabin crew (and most of the cabin for that matter).
3) Cabin crew tell him to turn it off, as instructed.
4) He ignores them.
5) A few minutes the later, aircraft stops on the taxi-way.
6) Announcement from the First Officer explaining firmly that we will continue our taxi once the gentleman has turned his phone off and complies with crew instructions.
7) Lots of tutting from passengers.
8) Lots of blushing from Mr Important.
9) Phone is switched off.
10) We resume taxi to the gate.
11) Mr Important is rather sheepish and surprisingly quiet when gathering his belongings to make his way off the aircraft.