So as I understand it I cannot make wifi calls from other countries TO the US since I'll be using a "compatible" phone.

If this is true how do I avoid having to pay for robo calls when I am out of the country? I usually put phone in airplane mode and use wifi when available and only put airplane mode off when I use data for maps, etc.

So I'll have to use skype to call to the US rather than pay .20/minute? (haven't used google voice but maybe that is also an option?)