S7562 new problem comes out ..

Dear team my s7562 have new fault comes when I making call incoming-outgoing sound ok but after 13-14 second it's muted or no sound in incoming or outgoing and same happened while using handsfree. But the call continues.. And after 3-5 seconds of the MUTE, again the call restores. Original OS was also done 2 times so far. Still the problem persists
Anybody solutions please help with a solution.,