I believe that you can never completely get rid of it, because any technical measure (signals jamming comes to mind) will interfere with the use of phones in an

I believe that you can never completely get rid of it, because any technical measure (signals jamming comes to mind) will interfere with the use of phones in an emergency, which trumps all other considerations. So the only way that I see is to make an honest connection with the students on a human level. This means they will probably keep the disruption to a minimum because they either want to learn, or because they at least do not want to interrupt the learning of others too much. It's not easy, but teaching well never is, and of course it is highly dependent on the students.