I chatted with Motorola, as I had this problem. Here is their response:
While on a call, press the center button(press the side only to the right) this will give you option to adjust the call volume of the phone......
So, the real answer is close. While on a call, you have to hold down the right outside edge, or ring, of the center key. While holding it down, turn up the volume button on the right side of your phone. It worked for me. Hope this helps!