Honestly I get the concept and why he wouldn't want anyone on the phone... But these are NBA players making MILLIONS of dollars with even bigger egos... Does he actually believe that Kobe Bryant will keep his phone off for 2 whole weeks cuz his coach said so?
He might be able to get away with this kind of thing in high school if he was respected by his players (although there would obviously be some or most that wouldn't obey this), but when you tell grown men what they can and can't do? lol, not gonna work.