AcerLiquid Z530 - disturbing Loud Static Sound heard by person on other side of call.

Recently switched to Acer Liquid Z530 and everyone I call complained off loud static sound while on call.Then I did all this :

1. Contacted Acer Support, suggested to Reset phone and run system update. But this did not help.

2. Contacted the Cust Support of both cellular operators I'm using. Did all that they advised. But this did not help. Also, swaped the sim - slots.

3. had a replacement garentee, immediately opted for it and got it replaced. I had an option for refund, but for my long custom for Acer, and was impressed with all other smart features of the phone.

4. Got the phone replaced with another one.

But, the new replaced phone also has the same problem.

This time did few more tests... The person on other side of the call dosen't here static sound if i switch to Speaker Phone or switch to Bluetooth hands free devise.

I managed with a bluetooth hands free for two days, but its a pain !

Pls help if any one has a better idea / solution. I'm looking for some useful tips before the expiry of the replacement Guarantee for this new piece as well :-)

Thanks !