This year I started a new policy from day one and it has been a success. I collect cellphones at the beginning of the period, lock them up and distribute them back at the end.
If we do something that requires phones (Kahoot, Socrative, etc) then I try to schedule these at the beginning or towards the end of the period.
This has greatly reduced students being distracted and honestly students have been very accepting of this policy. Many have even admitted liking it because they admit they are addicted to their phone and it is just too tempting otherwise.
At the beginning of the year if a student said they didn't have a phone I had a form for them to fill out and said I would contact parents just to confirm this was true. I had a few kids who once I said that quickly handed me their phone. I did of course have a few who challenged me but I explained honestly and openly that this is my policy so they had to follow along but also that it was a distraction and temptation. I am now 7 weeks in with this policy and it has been working great and no resistance from students.
A few things to help:
1) I bought a calculator holder and long strips of Velcro and folded it in half and velcroed over hanger.
2) I put a laminated number card in each numbered holder and numbered all desks. The desk corresponds to the slot the kid gets.
3) At the beginning of class students work on a writing or listening to authentic video and answering questions type of warmup and I tell everyone to place cellphones on desk.
4) I quickly walk around and hand out a numbered card and they give me their phone and I place in the corresponding numbered slot. (Many even say "thank you" which cracks me up)
5) I lock them up in the cabinet. For a class of 32 I am too nervous to hang them as of the weight so I fold it back and forth and place at bottom of closet which I lined with bubble wrap. It is important to the students that they are locked up.
6) Five minutes before class ends I grab the holder and stand up at the front and students come to me with their numbered card and in exchange grab their phone and replace with their card. If they are finishing up something I walk around to the desks and give phone for card.
No more confiscating phones, students being distracted during our conversation time, and more active participation and them really engaging with their classmates. I still do several activities that require their phones but I have clear expectations of when it is okay to use or not because if they don't need them they are locked up!