OpenPhone is a VoIP (Voice over Internet Protocol) application that 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.
If you have any other questions, please submit a request here. We're happy to help!