I used wi fi calling, my low cost carrier is Mint Mobile (it was acquired by T Mobile last year). The rates were super cheap - like calling a landline in Paris was 0.06 a min, cell was 0.02, London is ZERO, yes, 0 cost on any type. Hong Kong is 0.01 a minute both land and cell... etc etc
I loaded $10 in the account in 2022, and afrer multiple very long trips, still have over $6 left in the account. 
Of course the primse is, I rely on Wi Fi. Without Wi Fi, it is useless. But then it is more than sufficient for all our needs so no need for the major carriers' plans.
