I have noticed this to a small extent, when the phone and BT headset are on opposite sides of my body. The Plantronics Voyager 510 does work very well with this phone from my experience - and if you haven't already tried this BT unit, it might be worth taking a chance. I seems from my experience and that of several other posters that the 510 works well with the 6700 - and it is loud enough that you will need to turn it down, even with the old ROM (Verizon user here).