Default In-Call sound terrible on NAE

I'm on NAE firmware and did the unlock base on this guide. http://forum.xda-developers.com/show....php?t=2530610

I unlock the phone and was able to connect to T-Mobile. The one problem I'm having is that the in-call sound are terrible!!!!

I can listen to music and the sound is fine but when making a call the sound are very unclear.

Does anyone have any idea why?