Can't hear when making phone call

BTC460 connects fine with my phone & plays the music from it, however phone calls are so quiet. Please help?!

Maximize both the phone and music volumes on the phone. Control the volume exclusively with the car stereo. That should balance the volumes for both phone and music.

I have the BTC450 and I am having the same problem. The volume for phone calls really quiet and hard to hear. This model doesn’t have a volume button up or down. I have my phone volume all the way up. What do I do? How can I get it to where I can hear calls?