Might be a phone issue, rather than a car issue. I use the Treo and there is a button on the phone screen to toggle between BT Headset (in this case, the car) and handheld. If the call is on the handheld, you toggle back.
I hope, of course, that when you are reading the manual and entering the numbers for a pass code, you aren't on Route 78 of Route 24 Monday through Friday between 5:30 and 6:00. If you are, let me know and I'll take the service roads
