iPhone apps to make free international calls

On my iPod touch, I use GroupMe for SMS and Google Voice to receive transcripts of voicemail messages via email.
Both require a little bit of prior setup -- a google number, which is free, and setting up a Group in GroupMe, which can include any number of phone numbers and email addresses, including two (you and your interlocutor).
This is for non-Apple users.
For other Apple users, stick with iMessages and FaceTime over wifi.
Of course, Skype also works fine over wifi, too.
I suspect that apps that specifically hype free international calls are probably pushing advertising.

I use Skype often to call hotels to make reservations and confirm details, whether from the US or within Europe. Load free application, add a few dollars credit and call anywhere using a WiFi connection available free or at a modest cost at almost all hotels in Europe as well as some coffee shops, etc. Free to another Skype user (desktop, laptop, tablet or smartphone), just pennies a minute to anyone not on Skype. Phone and video calls. It works well and it's easy to use. There are other applications, such as Viber....a distant second for me.

You could try Viber, which I believe offers free calls via Wi-Fi, as well as free texts.

Viber (Free calls & message), StitMe(nonymous Encrypted Communication And Spam Call Blocking), Tango(Messaging) , And IMO(Free voice/video calls and Chat with emoticon) Thanks,