I know we ended with a hanger but just a little spoiler for everyone, he knows who’s behind the phone now and…
I don't think thats the case. In the preview (of ep 5), someone(i think the one who works for sa-eon) was telling him that the caller is a female and, i think we saw a shocked? face. So, i think he *doesn't* know who the caller is. maybe in the next ep, FL makes some excuse or something idk. Just a hunch. NOT SURE