So just received my phone today. (I purchased in the later batches)
I started it up, inserted the SIM from my Galaxy S9+, and actually followed the default set up.
After the basic Google start-up, I waited for the 'sync-ed' apps to download, and updated the phone to the newest version of Android. (Did not have 4G at this time)
In the settings, changed the Preferred Signal Type to 'LTE Only', restarted (acquired 4G at this point after restart)
I was not getting any phone calling service/texting without being connected to WIFI, so I *#*#4636#*#*, and toggled 'VOLTE Provisioned', 'V