OK - I got a better description from one of my callers - they say I sound choppy - kind of like bad conference room phones that cut off one caller if the other tries to speak.
I've found a place to post issues hopefully for HTC to see -
http://www.htcwiki.com/page/HTC+Mogul/thread
I haven't found a support e-mail address for them yet - too bad - it was easy to contact UTSTarcom