I finally got my AT&T iPhone unlocked so now I am learning about eSIM and how to use it when I travel internationally. It seemed straightforward - if your voice carrier/plan allows Wifi Calling and you have Wifi or Carrier Data connectivity on your phone, the voice calls will work.

Reading this thread, it seems it is not as simple as I thought? I didn't even know what IMS means and had to look it up. It is basically sending everything through IP, right? Isn't that what they do now anyway even when on cellular (i.e. VoLTE)? What am I missing?

Thanks.