Kent RO — Free Service Not Provided

I bought kent RO from a local vendor last year. It is out of warranty but i was promised 4 years of free service. I didn't get any warranty card in the box whenever i purchased the product. I have original bill with GST. Whenever i registered first time for free service, they are asking for charges as i have not warranty card. I am asking for first service. How can one deny free service if i have original invoice copy. No other company deny for it. This is clear fraud with the customers. They are asking for money for service & change of filter etc which must be free during 4 years of free service promised. Please look into this matter & take strict action against Kent