We just got back from a quick trip and we like to keep in contact with the kids while we are there (even if we are only gone for 4 days.lol). We downloaded Magicjack to our phone and you can call the US and Canada for free. You have to have wifi (or turn your data on, but that would charge you, so defeat the point) and you can call for free. Was very handy and worked like a charm. You can also receive calls for free, but you have to set it up and we didn't do that since it was a quick trip and we only planned to call the kids a couple times.
Worked like a charm and thought that might be helpful for anyone looking to call home for free:)