Facebook retools messaging again by adding calling to main app

Facebook Inc. is bringing voice and video calling to its flagship social networking service, the latest attempt to fine-tune its communications features after spinning off Messenger as a separate app in 2014. 

Some users, including those in the U.S., will be able to place voice or video calls from the Facebook app beginning Monday. The new feature is just a test, but it’s meant to reduce the need to jump back and forth between Facebook’s main app and its Messenger service, said Connor Hayes, director of product management at Messenger.  Facebook also started testing a limited version of Messenger’s inbox in the core Facebook app last fall.