Hi Floydtp,
Sorry i can't be much help considering I don't even have BT in my 06 X5, but what if you turn BT off on your cellphone when you need to take private calls. That's what i would try.
I have a few questions about your X5 if you don't mind...

Do you have a ULF or TCU, is it located in the cargo area, latch compartment on
drivers side?
Do you have steering wheel buttons and SOS button on the head panel?
Do you have center console pairing button?
Do you have Ipod plug in the golve compartment?
Just really curious and trying to figure out what type of retrofit I will go with. Thanks for help.