Why does my '07 Camry's Blue Tooth system ring when I pass someone else's car with BT/go into a new area code

I have a Samsung A-920 mobile phone that is paired with the car. My phone has the visibililty setting as Hidden. Samsung says there are no problems with this phone. It uses Blue Tooth Standard 1.2. Both Toyota and Sprint deny any responsibility for the ringing. This happens regularly when I cross the bridges in the San Francisco Bay area, go to other counties which have different area codes. It also happens when other cars pass me. The event is: the phone rings once, the display shows "private", and then it is done. But this can happen multiple times, depending on how many people drive pass on the way to work or to other destinations. It is annoying and disruptive, and potentially dangerous. Thanks for any advice on how to stop these events.

Why does my '07 Camry's Blue Tooth system ring when I pass someone else's car with BT/go into a new area code
Seems to me this a bug with the phone -- it should be able to ignore these extraneous signals without ringing.