We don’t allow any electronics during our exams - if caught using one during the exam, the student is assumed to be cheating. The students are told about this exam policy ahead of time. All bags must be on the floor. Only items allowed on the desk/table are writing instruments, straight edge, water/coffee, and depending on the course, maybe a non-programmable calculator. We ask the students to turn in their phones when taking a restroom break, and keep track of how long they are out of the room.
We had to implement these proctoring rules a couple of years ago because several students complained about other students cheating on their cells. And these were grad students - it’s probably even worse among the undergrads.