Comment by objectcode

VoLTE is normally for both inbound and outbound. It is not 4GLTE base functionality, but is available if the phone supports it on the carrier and the carrier supports the use of it. An alternative is CSFB, which is about switching to 3G/2G (where calls are base functionality) for the duration of the call, but 3G/2G is not available everywhere. VoNR is like VoLTE(the ability to make and receive calls on 4GLTE), but for 5GNR. The carrier's equipment can find the phone for example by the phone sending tracking area updates/location area updates so it "knows" where the phone can be asked to connect so it can receive an inbound call etc.