Apple India — iphone 7 heating issue

Address: 560047

I have bought iphone 7 within 2 days it started heating up badly while using apps i gave it to the service centre they took almost 12 days to resolve and was not updating me with mail or any follow up call after 12 days of running behind this they said it was something to do with hardware gave me a new replacement product which is refurbished now i have used this replacement again for few days and it’s still heating up. I paid all my saving s to buy this and this is what happen
I need an answer to this