I recently had the same issue, and googled "screenplay format phone conversation." -- lots of stuff, like this:
Here's the definitive guide on how to write a phone conversation in a screenplay: the three main methods used by pro screenwriters.
www.scriptreaderpro.com
My first instinct was something like this:
EMILY
Yea I know. electricity
(pause, listens)
Oh you're the water one.
(pause)
...
But the guy in the link doesn't like this. Maybe just eliipses
EMILY
Yea I know. electricity...Oh your'e the water one...
Or maybe a mix of the two, with just one first parenthetical. Either way, the point, I think, is to just make it like regular dialogue. The "*the caller talks"* line is almost certainly not correct, using up, as the guy says, "valuable real estate."
My problem was with a two-sided phone conversation, and the answer is to establish the first scene, with a scene heading. Talk. Then the second scene heading. Talk. then type, in caps to the left, INTERCUT, and just go back and forth.
There is, I think, an elegant solution to these little formatting questions, usually following established conventions, so that you sound professional. You'll get there
