Sound quality while talking on the phone

I just picked up my Solstice over the weekend. I'm replacing an older Sony/Ericksson W300I. My Solstice sound quality does not sound as good as my old Sony/Ericksson. The caller sounds like they are talking in a tunnel or a hollow can. One person I was talking to said they could hear a repeat of what they just said to me on there end. I like everything else about the phone, well the keyboard could be a little bit bigger, but overall the phone is ok. The sound quality of the phone is disappointing. Anybody else having any problems? Maybe I have a bad phone? Maybe the Sony was that much better? Any ideas?