Ah but did you buy the car because it had the handsfree kit for your phone or the phone to fit the handsfree kit in the car?
I bought the phone first, then an SLK 320 which I had fitted with the full Nokia CARK-91 handsfree system. Worked fine, except that the speed bumps and cratered Oxonian highways eventually loosened a plug somewhere in the system, so I took it back and asked them to make sure it was fully secure.
Sold the SLK320 for an SLK32 AMG and bought another CARK-91. The fitters said that it was a right $od to sort out, because the AMG has a weird Bose system and they had to faff about with various adapters etc. But it's been fine now for nearly 7 years. As indeed has the Teutonic tourer!
When I attended various Airbus meetings a couple of years ago, it was interesting to see how many of their senior people still used their good old Nokia 6310i phones rather than gimmicky girly smartphones!