FaceTime
Depending on who you’re trying to call, you may not even need to download a third-party app to make an international phone call. Apple’s own FaceTime service lets you make calls to other Apple devices free of charge, as long as you have a Wi-Fi or cellular data connection.
Of course, the only downside is that the call recipient needs to also have an Apple device. Luckily, there are several that support it, including iPhones, iPads, iPod touches and Macs. And while FaceTime is famous for its video-calling, keep in mind that you can make audio-only calls as well.