If you have characters who speak to one another through mental telepathy, the Dialogue will be somewhat unique.

Look at the example below:

Even though the characters are in the scene, all the audience will hear are their voices. Therefore, I used the Voice Over Character Heading extension.

Of course, if you want to be 100% sure the reader doesn't get confused by the (V.O.), you can add a parenthetical. After all, a reader might just assume the voices are coming from unseen narrators, or characters from a scene following the current scene.

To alleviate confusion a writer could do this:

Of course, that would get old real fast. Even if you have telepaths in your film, keep this sort of Dialogue to a minimum.