phone in the arm rest ??? how does it work?

[Rabbit]

hello all. im sure this has been ask in the past but cant find what in looking for in the search.

i have a 2003 x5 and it has the the phone cord in the arm rest. i have a phone for it. but it does not make calls,

can it use the kit that is on ebay and add an old i phone to it and make it work?

can i get un unlocked motorola phone and make it work?

how can i get the phone in here now to work?

what does it do? does it go threw the speakers or is it not worth messing with?
thanks