http://s27.postimg.org/mt2my7xgz/Sam..._Handset_M.png
Here is your solution bro....
****any single step can solve your problem.
try this one by one.****
Primary option :
1. You can check in function GOTO > Setting > Accessibility >Turn off all sounds
(please uncheck this option)
2. when in call, press the touch in left of the home botton ( that touch usually is not visible ), than u will see " Noise reduction off
3. make wipe data reset
software options :
01. Flash with this version. I9300XXELLA_I9300OXFELL1_ I9300XXELLA_HOME.tar.md5
02. flash phone with Australia Generic Retail firmware
03. flash with 4.1.2 will be allright
04. flash with 4.2.2 work for me with 2 i9300 i try it
05. 4. EFS must repair
Hardware options :
01. open your phone and remove charging base connector and check head set working or not, if yes then replace charging flex.
02. lcd problem so much copy lcd in market thats not orignal change orignal then working perfect
03. you have to rehot/resold or change 604 ic.
Be carefull when changing this,
that theres baseband ic opposite site of board.
It may cause imei null..
****** don't forget.samsung used very very soft glue.it s not too hard.only you must be a little carefully.thats all*******
Let us know if problem solved