Viber
Perhaps not quite as well-known as WhatsApp, Viber is still a popular choice for cross-platform and international communications with more than 1 billion users. Like other apps on this list, you can send text messages and make audio or video calls for free, as long as the recipient is also a Viber member.
But even if they aren’t, you still have some options. The Viber Out feature lets you make low-cost calls to landlines. Sure, it isn’t free. But it could save you some money on international calling in a pinch, particularly as it’s likely less expensive than your carrier’s international rates. Viber also has a number of encryption and privacy features to boot.
Get Viber here.