MI POCO - The mobile i have received is of a damage product

I have ordered an MI POCO phone via flipcart. And i have been using this phone, suddenly get an issue with network and calling. I proceed to service center and they call it an issue with mother board. And they replaced it. After one month of replacing, i face the same issue. My phone is under warrenty. This issues i have faced during six month.
Now my question is ...
*. Why the brand is selling damage a product to earn profit?
*. How come I repay the damage?
*. Is the company so called MI needs to get a social media recognition for damage product and nonsensical customer service?
*. Does flipcart sells MI damage product habitatly and making the company's worth high?
*. Can i get a satisfactory outcome from the company?
*. How can i use it if every next day it shows problem?
Get me a solution ASAP.
These conpany are of no use in india if customer dont get satisfaction.
Look into the matter and try to sort it out.