Android Zello works with WiFi, but not with data
You may not have a mobile data plan enabled or your settings may not be changing. Open Settings > Mobile network. Make sure the mobile data option is turned ON.
Also open “Access Point Names” and make sure that "Internet" APN is enabled. Choose "Internet APN” and verify that the configuration matches the APN required by your service provider.
Questions? Submit a new ticket for support-related inquiries.