Havells India — Experience with First service within One year of purchase

I purchased one Max water purifier in 30th Sep 2019 in Kolkata. I stay and work in other city and hence come here once in a while. Last week (Aug 2020) I called Havells for my first service. The service person did a general service but refused to change the filter as it will be done in "9 month service". I argued with him that it is already 11 months over and hence he should do the change. He he had a funny logic that I will have to raise another service request for this. I do not understand what type of logic is this? Is it from Havells itself or it is coined by the service person to avoid changing the filer. I want to know what are my entitlements (which filters will be mandatorily changed) in first year?