Just be aware (and I'm sure you are) that Wi-Fi calling (using the phone, not a program like Facetime or Whatsapp) "costs" you minutes just like a regular phone call might, ie calls to and from a US Number are free, however you'd be charged minutes at the applicable rate for an International Call.

https://www.att.com/shop/wireless/fe...i-calling.html

https://www.t-mobile.com/support/cov...-from-t-mobile

https://www.verizonwireless.com/supp...-calling-faqs/

etc etc.

Moral of the story is, when in doubt and dealing with any kind of international phone call, use an app like Whatsapp to make the call. I learned the hard way a few years ago!