Rather than add an edit to a long post, this is my current preliminary findings as it relates to the original thread subject of 12-30-23.

Since I now seem to mysteriously have WiFi calling enabled, I have been able to make 2 WiFi calls on my US Mobile line to foreign numbers while roaming in Thailand. I have successfully called Thai Airways over IMS (T-Mobile Data), and also an independent WiFi network. These calls were to +66 XXXX numbers, which is the country code for Thailand. I was able to switch to the English menu and step through the first few options in a call over a minute long. This seems to confirm what I had been told by their rep as an included free feature.

I intend to explore this feature as much as possible in the next few weeks. If it is what it seems, it will be a real game changer for travel communications. Imagine having a low cost alternate line that gives not only international free WiFi calling, but also may be used with or in lieu of IMS for US WiFi calling.

In summary if you don’t care about the details, here is what MAY be possible.

Be able to set up a dual sim phone for free calling to and from US number prior to departure.
Set up the same phone for free calls to foreign numbers while in a foreign country.
Have a phone with Verizon voice & text and 2Gb of Verizon data for the US @$10 a month, inc. taxes and fees.
Retain the use of any roaming data service you prefer for overseas use.

As serpens alluded to very early on, this may all be “Too Good To Be True”, but time will tell. It certainly is interesting to explore.