OpenPhone is a VoIP (Voice over Internet Protocol) application which uses your data plan when you're not connected to a wifi network.
Using your data minutes to make voice calls is a lot more efficient than streaming video.
A minute of an OpenPhone call uses 0.5 MB of data. This translates to 250 MB for 500 minutes of talking.
It's comparable with the data usage of music streaming applications like Apple Music and Spotify.
Have any questions? Let us know!