[Nucking Futs!]

So everytime I'm on a phone call (in bluetooth mode) then I turn off the car (hit the engine start button twice), everything turns off except for the bluetooth when I'm still on the call. In my friend's Lexus & my other vehicle w/an aftermarket headunit (w/bluetooth), all you gotta do is tap a button on the screen to transfer the call to the phone & then turn off the car. I did this (transfer call to phone) but yet when I hit the engine start button to turn off the electronics, it won't let me since the screen is still in bluetooth mode. My question is, what am I doing wrong here? When I get out of the car, I really don't want to tell the person on the phone I'll call them right back just b/c I have to hangup the phone (while in bluetooth mode), turn off electronics (hit engine start button) then call them back. Thx!