Anything on Entune that requires data will use the phones data plan. Streaming Pandora, iheartradio, stocks, weather, bing search and I believe traffic info as well. If you don't have data plan then don't use entune. Uninstall entune app from your phone and use your phones music player to play music. There's no album art.
No, Bluetooth does NOT use your data plan. It is only the protocol for the connection between your iPhone and the radio. As you are aware, you can play music that is locally stored on your phone to the radio via the BT connection. But if you use the Entune apps that consume data (Pandora, iHeart, Weather, etc.), your phone will use its data connection to server the requests to the apps over the BT connection.
BT connects car to phone. Phone to internet uses data plan. Internet radio station and other apps that use internet will use phone's data plan.
If you configure internet, but don't plan to use the apps I would think the main thing that might use data without you noticing would be the traffic info for the maps. System updates (when available over the air) will also use data.
When you pair the phone to the car, you can choose to use the following three: - Music - Phone (voice) - Internet (data) If you have Internet (data) disconnected, I think you are safe.
