Could you make lessons that use the devices? If the device (and student) are actively using the device then (maybe) they are less tempted to use the device for something else. This could be live streaming of content, or writing a program to simulate a bacterial plague in a petri dish. If we are all writing R code to analyze a data set, then stopping to take a call will result in being completely lost in the class when you return from the call. Most students should be able to figure that one out.

You could try messy: Pottery is easy as a good student actively participating in the class will be covered in mud. If they pull out the smart phone mud gets everywhere.

Increase the pace of class, and test difficulty. If they are madly trying to write what was just on the chalkboard, they do not have time for a smartphone call.

Give a presentation on what you expect of phone use and common courtesy. You get that sort of thing in movie theatres before each feature presentation.

I have attended a few college classes. A small number of teachers had a charisma about them and a pace of class that kept me at the edge of my seat every lecture. Others, I often wondered why I even bothered attending class. The teacher read from the book and the test was from the book, and it seemed kind of like the teacher did not really want to be there. Hired for research and forced to teach something to fill out their promotion and tenure packet. Be charismatic (yes, easy to say but I never found the Charisma 101 class in the college manual).

A Faraday cage. A fine mesh copper screen over the walls of the classroom and properly grounded will largely take care of the problem. Window screen made from copper will work.

I can agree with Tim's answer about incorporating a Faraday cage or a signal jammer in the class.

My suggestion would be to encourage the students to record the class session by either voice or video. My sons high school teachers has their students interact with their phones by having them look up information during the class. These suggestions cause the student to interact with the teacher (Professor) and their hand held device.

The following is a lengthy quote from Soegaard, M., and Dam, R. (2013). This is not the norm of this person's quotations of authors. However, this particular quote seemed appropriate at this time.

“The flower of computing is borne of many disciplines but belongs to none. It is a new discipline in itself. For it to bear research fruit, its academic parents must set it free. Let us trade knowledge not dominate it. By means of different terms, models and theories for the same subject invite confusion. Universities that split computing research into small groups, isolated by discipline boundaries, distance themselves from its multi-disciplinary future. Until computing research becomes one, computing theory will remain as it is now - decades behind computing practice.” (Soegaard & Dam, 2013)

Be ever charismatic to maintain students' interest in learning during classes. Have a mix of teaching approaches. Keep updating teaching/lecture materials...

Vincent Raphael Nyirenda, can you make a decision to be charismatic? Will your charisma be the same for all students?

Is charisma nature or nurture?

It cannot be the same for everyone otherwise Trump would be loved by all or have never gotten out of the swamp where he came from.

However, there are a few that have enough charisma that they go into a grocery store and everyone is their friend. I am equally certain that if all of those people really knew the charismatic one the charm would wear off for some.

Timothy A Ebert, maybe charisma is like beauty, or leadership? Not a personal trait, or a skill, but a perception or an assignment by others?

Obviously it is a perception by others, but there are still people who are better able to make a great first impression.

Simply make them crazy to their research work rather than smartphone!

If students are paid to learn, they will follow instructions much better (including putting away devices and other distractions) and will learn more with less instructor effort. The difference is night and day, based on my experience and observations.