Motorola Electrify :: Routing Calls Through Car Speakers?

I have the phone in the dock, and I have the audio cable going from the charger to my car's auxiliary audio port. When I try to make a call, the phone defaults to speaker phone. In a noisy car environment, it makes it difficult to hear the other person well. While the call is going on, there's a "speaker" button in the bottom right on the phone which I can press, which causes the audio to be routed through the car's speakers as music is, which is great. However, doing so causes the person on the other line to no longer be able to hear me. I just upgraded to 4.5.1A_SUN_USC19.0 and the problem still remains.