OnePlus India — Delayed in repairing of OnePlus Y1S TV

I have complain regarding TV more than month ago, after being complain register the engineer visited and check the issue. The problem he detected was motherboard was not working and need to change it. It's been more than a month for the last visit but the has not been resolve. They make excuse of non availability of required part. I have called and texted multiple times in a month but no satisfactory response I am getting and no resolution of my problem. Also I am loosing the period of warranty. The TV stop working after a month of purchase so I also not have trust on this piece, so I also requested from them to change the piece if problem is not solving. But the company also rejected the request. I am requesting you please help me, this daily thing also deteriorating my mental piece. Thank you