That's a great question! So if anyone attempts to call their phone, it won't be able to connect to them directly. However if people would like, there can be a pre-recorded message or video from the four's shadows - basically just like what they'd show on the Midnight Channel in Persona 4.

Speaking of, anyone who has the Midnight Channel TV gacha item will also see these recordings pop up on their televisions whenever it rains in Kaisou (which will be happening pretty regularly because it's April)!