I figured it out what you need to do is activate your design 4g and then factory data reset i swear
Ok after all the replacements the problem was so simple i could not believe i did not try it before ok. So what you do is activate your HTC EVO DESIGN 4G for the very first time then do a ''FACTORY DATA RESET'' You know just wipe the phone and everything off it now try your phone calls i swear it worked for me now people tell me i sound fine no echoing no fuzziness no low far away sound. I feel so stupid for getting all the replacements.
Try it and let me know if it works for you.