Xiaomi India — mic problem in note 4. defect product given by store

Address:	Hyderabad, Andhra Pradesh, 500032
Website:	Mi india

Hi,

I have purchased mi note 4 64gb on 6th april 2017.
But i received defect product.
Mic not working properly.

I guess many of the phones havibg same problem.
But my question is company distributed this handsets to market. And when i approached customer care they are saying like mic need to be changed.

How can a new phone spare part will be changed with no problem from my side.

I want urgent resolution for this.

Regards,
Rakesh