i have the jawbone II. even on the lowest volume setting, it is initially amped for less than a second after making a call and then returns to the setting it was on beforehand. it hurts my ear.
also, sometimes i have to click on speakerphone and back to bluetooth to get any sound from my jawbone.
Hit the green call button to bring up your call log. Hit menu>options>general options. Set default call volume to "Previous" It will then be at the volume you had your previous call to. My guess is your is set to 100%, so even though you turned it down for a call, the next is again at 100%.