I am a little confused by Tom_MN's comment. If you call from an app, such as WhatsApp to someone else with that app, yes, I think you will not have to pay for an international connection. (This is true with Skype to Skype, Google Duo to Duo, or other similar apps.) A wifi call to a non-US number is treated by your phone carrier the same way as if you dialed it using a telephone-type connection (i.e., not a data connection). The fact that you make the call using wifi does not save you from the cost.
And, if you are looking to use wifi to make calls to another country (even if you are physically located in that country), there are less expensive ways to make a call. Skype allows you to call foreign landlines and mobile numbers at rates much lower than Verizon, AT&T, and T-Mobile. Pennies a minute versus anywhere from $0.25 (T-Mobile) to $1.00 to $3.00 (AT&T) (Pay-per-use rates). I have a Google Voice number, so I make wifi calls to international numbers using the Google Voice app at pennies per minute.