As someone else mentioned, I would suggest a test call with the air fans off (AC/heat) in your driveway (no road noise). If there is still a lot of noise, then there's definitely a problem with the phone or the mic in the car.

To figure out which, I'd suggest borrowing a bluetooth headset and seeing if a different bluetooth source (mic) eliminates the problem.

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1995 BMW M3 (Track prepared)
2006 BMW 530xi (Wife)
2011 BMW X5 35d (Tow/Daily)