Sona Water Solutions — Service with in warranty

I bought water purifier from Sona water solutions Bangalore in the month of Jan 2020 and i have very bad experience on providing the service. My water purifier given problem within 4 months and once i serviced and paid for it again it started giving problem with in 3 months and now engineer is asking for Rs 3500 and says no warranty and need to take AMC but im trying to reach there office numbers updated in invoice always switched off and the person installed mobile number is not valid they trying to cheat people with different address