I've had two H700 headsets. When I upgraded my cellphone, people would say they could not hear me clearly with the headset that I sounded as if I was at the bottom of the barrel. However, they were very clear to me. No amount of adjustment could fix this. Since I had it for three years, I didn't mind replacing it with a new one. So I tried a new H700 and people were hanging up on me because they couldn't hear me at all. When I took it to the cellphone carrier to determine what I may be doing wrong, it was determined that it was not compatible with my new phone. I gave it away and it works great for the other person.