ASUS - ZenTalk

Could anyone share the information that which carrier in US supports VoWifi for Zenfone 8?(very upset, just found the T-Mobile and its MVNOs banning Wifi Calling of Zenfone 

I am super happy to see a new Zenfone promotion which can save me 50 USD,BUT I just got noticed that the Zenfone online store in Taiwan would even provide a free extended warranty for half a year! Why don't we have the *same warranty policy*?!"Rumor"...