I use mi5s plus by skt(sk telecom) in south korea.
But I have problem in call.
my phone is mi5s plus
★★ SKT (MI5S PLUS) -> SKT other phone
MI5S PLUS (VOLTE mark(O), HD mark(X))-> SAMSUNG GALAXY5, GALAXY7, GALAXY7 EDGE, ETC (3G(O), HD mark(X))
MI5S PLUS (VOLTE MARK(O), HD mark(X)) ->...