CaptionMate calls connect via the internet. To use the app, your device must be connected to the internet either through Wi-Fi or cellular data. The way the app connects depends on your device's connection settings.
Please note that if your phone is not connected to Wi-Fi, CaptionMate will use your cellular data. As CaptionMate uses only a small amount of data, it is unlikely that using the app will cause you to exceed your data plan.