Pureit / Hindustan Unilever — Faulty product replaced with a faulty product

I have purchased pureit water filer on 29-Sep-2018 by paying 16200. Within two months, water was leaking from the unit. The unit was replaced with a unit that was manufactured in May-2014. Now the unit does not work. Unnati, their agent in Hyderabad is asking me to pay Rs7000 towards replacing a control module. Within 2 years, I am being asked to pay Rs7000 towards maintenance of a product that costs 16200. The faulty product manufactured in 2018 was replaced with a product manufactured in 2015. I bought the product two years back. Now the product that is installed is more than five year old. Obviously it will develop issues after five years!!. Pureit is simply forwarding my request to unnati, who is a dealer in Hyderabad.
Pureit has maintained that paying 7000 towards maintenance of a product that costs 16200 within two years does not make sense.