I am no parent, but if they took away the cellphone permanently, I would try to fight to get it back (to return to where I got it from in the first place), if that doesn't work, deactivate that phone and not get a new one, at least for a moment of time. Kids need to learn, first.
If they took away the phone for a moment of time, and I hear about it, depending on the circumstances, I would either do nothing or take it away for a longer period of time.