This is a weak reply, and is misleading.

I had to get a T-Mobil Sim card due to traveling in a place with no Verizon service.   I pop the sim card in my unlocked, samsumg direct purchace S9+,  first thing that pops up-  Wifi calling is on!  The android menu  under advanced features now has all of the wifi/HD voice options that disappear when my Verizon sim is in.    Verizon is suppressing it, not the phone, not android.