2. Whatsapp Messenger

If you are living in the 21st century, you must have heard about WhatsApp at least once in your life. It is one of the most widely used messaging apps across the world. It lets you text, audio/video calls to others on your contact lists using Whatsapp. You can also share images, videos, documents, and your location.
Apart from these, you can share your daily status that will be available for the next 24 hours. Whatsapp uses end-to-end encryption to take care of your privacy. This means, all your messages and calls are kept confidential between you and the receiver. No one other than you two can access them, not even Whatsapp itself.
Download (Android | iOS)
3. Google Voice

Google Voice is surely one of the best voice calling app you will ever have. It offers a completely free service where you are given a different number through which you can call and text other people. The fact that the other person can receive your calls and messages even if he hasn’t installed the app makes it appear more useful. Moreover, another benefit of this app is it won’t bore you showing boring ads.
Apart from these, Google Voice comes with some amazing features like transcribing voice mails into texts. This feature is useful when you are in a crowd, and someone sends you a voice mail, you can just view it in the form of text rather than trying to figure their voice. However, the only disappointing thing is, it is available only in the US and Canada.
Download (Android | iOS)
4. Facebook Messenger

Facebook is probably the most used chatting platform after Whatsapp. And they do offer quite a decent service even though they are a bit slow and consumes a lot of data and battery as well. The Facebook Messenger allows you to send text messages or make both audio, video calls to other users. You can even stick to group video chats with multiple users at once.
What’s interesting in this case is, unlike WhatsApp, you can even talk to strangers who aren’t in your contact list. Just make sure the other person is added to your friend list, and that’s it. You can start a conversation at any moment without paying a single penny.
Download (Android | iOS)
5. Viber

Viber can be considered as a replica for WhatsApp, though it is not very popular in comparison. But it comes with some of the exclusive features that let you easily manage your data. Like Whatsapp, Viber also uses your contact list to verify users. You can send texts, make calls to the ones from your contacts who are on Viber.
On the other hand, it even lets you take backups of your messages and sync with other devices seamlessly. You can simply scan the QR code and log into other devices. This will ensure you don’t lose any previous data of yours. In order to make other international calls, Vibe lets you buy credits for them too. And like most apps, you get a group video calling service for free.
Download (Android | iOS)
Conclusion
A free calling app can be helpful at times when you might run out of your main balance or suffering any kind of network issue. All the names mentioned above does a similar job, but they differ based on a few functions. We would suggest you try Whatsapp or Viber before the others. As they offer a much stable and consistent service, there are high chances for you to like them.