Question Regarding Use of BT w/ Car Stereo
 

I just installed a new car stereo that has built-in bluetooth, which allows me to stream music from my phone and take calls through the stereo. It all works great except for the built-in mic on the stereo. I can hear the person on the line just fine, but since the mic is on the face of the stereo itself, they have a hard time hearing me. Is there a way for me to receive calls through the stereo, but use the phone's microphone instead of the mic on the stereo? I have Sprint TP2 with the stock ROM. The stereo that I installed is the Dual XHD7714. Any help is appreciated.