[He manages, just barely, to hide his amusement when Zagreus speaks to the phone like that. Admittedly he had done the same thing, but he doesn't say that. Instead, he rests his own device in his hand and slides his thumb across the screen to bring it to the same point as his companion's phone.]

They are primitive in that regard. You need to write the message using the letters on the screen. They call it 'texting'.

[And he sends a little message, which pops up on Zagreus' phone a moment later.

Hello.]