When I enter my car, the bluetooth connects automatically.
How can I continue a conversation on the phone, when I exit and turn off the engine?

It will automatically switch over the conversation to the phone (speaker) and not drop the call.

Although the phone is supposed to stay on the call even if the bluetooth has been disconnected (when the car is turned off), it does not happen on my 9780. Is there anything I should set up differently on the phone?