What are the different ways to have characters talk on cell phones?

There's a term called INTERCUT which is used for when you're bouncing back and forth between two locations (like when you're writing a phone conversation).

From the Standard Guide to Script Formats:

Quoted Text INT.  JOHN's LIVING ROOM John is on the phone talking to Martha in her parlor. INT.  MARTHA'S PARLOR Martha is obviously upset by what she hears over the phone.  INTERCUT Martha's reactions with John's conversation in his living room.

At this point, you just write the dialog without saying that you're switching back and forth.  You don't include any more headers, though you should include some action with the dialog.


Phil

There's also when you're only showing one character on the phone, and we don't hear the conversation on the other end.

Say, for instance, you've got a guy on his cell phone and he's receiving bad news.

JOHN (ON PHONE)
What?
(pause)
Oh, my god...

Anyway...there are different ways of doing even that simple bit.  Some folks might replace with "pause" with "beat", or may imply a pause in John's end of the conversation with ellipses.

I'm not sure if there's a single, universally accepted way of writing that kind of thing but if anyone knows it, please share.