HTC 2125 / 2100 (Faraday)

I'm using a Plantronix Voyager 510 bluetooth earpiece with my 2125. All is good except, I cannot control the volume with the phone, I have to use the volume toggle on the earpiece. I have used this Plantronix with a Nokia 6620 and currently use with a Blackberry 7250 and when I changed the phone volume (while the earpiece was active) it would change the Plantronix volume.

Anyone have an idea how I can get the phone volume control to change the earpiece volume?

Thanks,

Twdix