I was experiencing really low volume with my F700BT during bluetooth calls. I had the volume setting on the AVIC set to the maximum, and the phone was still a whisper. But I recall reading a post on the forum saying to check the cell phones settings...and loe and behold...I found that the "bluetooth volume" setting on my phone was really low (say 2 out of 8 ). When I raised it to 5 or 6 out of 8 it was perfect.
Now, I could not find a way to set the "bluetooth volume" on my Samsung R500 phone unless the phone was connected to the Pioneer unit (i.e. AVIC running) and I was in the middle of a call. Maybe there is a menu option, but I could not find one. In any case, while talking I just activate the button to raise the 'phone' volume and the sound from the AVIC unit goes up. Now my calls are all crystal clear, and I could lower the 'bluetooth volume' on the AVIC a few steps...so the "+" "-" buttons on the call box (on the screen) can be used to adjust the volume once again.
Cheers,