Congregations seeking to transform do not ask people to turn off their cell telephones and tablets during worship. Yes, they do ask them to silence them, but not to turn them off.
Instead they ask them to use their cell telephones to make an offering, access You Version or some other Bible application for the scripture being read, take sermon notes, click on the QR code on the worship bulletin/folder to see announcements, access the church web site and register for an upcoming event, text about the sermon, music, or some other aspect of the service, and other things.