I do my best to establish a culture of "be busy" and it takes a long time. I do occasionally have to make someone put their phone in my famous phone time out box and that makes a few others put it away.
An occasional email or phone call to a parent to let them know that it is impeding their learning (or sometimes the learning of others) is also helpful.
We will never win the phone battle, but persistence and conveyance of understanding why we shouldnt be attached to them non stop during class is the most important tool. Keep up the good work.