In one of the past updates of Facebook Messenger, was added the ability to make voice calls using the same application. In beginning this feature was only available in USA and Canada, but now few more countries are added in the list.
Facebook Messenger is in my view an excellent alternative to WhatsApp, available only to users who have access to the popular social network. Among the features that are not present on WhatsApp, is the ability to make voice calls and this was added in recent months in Facebook’s Messenger app.
The situation appears to be changing, since this new feature is also enabled on clients of the United Kingdom, working both via WiFi and 3G. We have no certain information at the moment, but assume that the service may reach very soon in other parts of Europe.
According to Pocket-Lint, the service is still in experimental phase, and you can run into problems and inconveniences, although those who have tried it are very impressed.
Voice calls currently work only on iOS client, while still have not been enabled on Android and other platforms.