Maybe you don't know what a “dumb phone” is, but your teens certainly do – and they don't want one.
One of my closest girlfriends hasn't upgraded to a smart phone yet: her trusty old flip phone serves her just fine. She does find herself several times a day, however, constantly apologizing for her lack of connectivity.
If we're in a group and someone says, “quick, grab your phone and take a picture!” or “get on Facebook to show me some pictures of your new niece,” she has to shrug and say, “Sorry, I can't. I have a dumb phone.”