Havells India — Warranty and AMC

I have a Havells Water purifier which is still under warranty, upon asking for filter cartridge replacement as the cartridge life is over. The technician and the person in charge are asking me to pay for “AMC” of amount 6000rupees, which is basically extending the period of maintenance for one more year. They are saying without AMC they cannot change or replace my filter cartridges.
I am so confused, as my product is still under warranty and I have to pay extra for replacing the filter cartridges.

I want to ask Havells, to elaborately explain, what are the free replacements offered during the 1st year warranty period after the purchase of the product.
The technicians are just confusing me saying, so many things but are not clear about the warranty period coverage.