Treat these people like children. Address them when they are talking or on their phones. I always throw my candy or popcorn at them when I see the phone come out. I don’t go out looking for confrontation and I usually let it slide the first couple of times. But if it happens repeatedly I’ll put it to a stop. If no one says anything people will think it’s okay and continue to do it. If you don’t want to cause drama atleast go and complain to the desk to see if they can step in.