Hi Guys,
Well I fixed this issue.
These are the steps:
This code *#0002*28346# has
[1] Debug Screen
[2] Version Information
[3] RF test
[4] UMTS rf nv
[5] Read gsm rf nv
[6] Write gsm rf nv
[7] Base Band
[8] Audio
[9] Common
I this screen go to "8" Audio.
Next "3" SPK Config
Next "6" AV-AMR
Next "2" SPK AMR Codec Gain
Here both "txVol" and "cod_tx" were set to "0db", I changed it to "10db" and it fixed the problem

Remember to do Load Params by going back to SPK config.
Hope this info helps someone.
Regards,
Geethesh