Your Existing system maybe outdated....

remember the motorola phones that came out after the infamous "Startac" phones? think they were the ( V phones with the silver-Steel Back)

Well like i said if the 1st Oner got the vehicle with a phone Activated V phone or star tac phone then that " Phone-button" would apply...

Also Phone cradle would probably be inside center console area and you wouldn't miss it cuase you would see impint of where a phone wouls slide into you would see the "copper connection that would charge phone.

BMW does have an Accessory that old BMW owners that had the old phone cradle phone installations already installed. it's a Egg shapped bluetooth device that slides into the old Cradle and would "pair" with any NEW Bluetooth compatible Phone ont he BMW website List....

But like i said you would probably need that installation (cradle) already
there.

there are several options i hear owners that use 3rd part installations.. just do alot of research prior jumping into something that maybe to costly..

I know "Belkin" has a Bluetooth Speaker Device that allows users to use the speakers as Listening/talk Devices it's an Egg" shaped Device Wireless FM modulator ---- research it

and Good Luck!