Nokia India(hmd Global) - Service Denied under warranty

I purchased a Nokia *.* plus from Flipkart on **th Feb **** under order number OD******************. In the month of August, the back glass cover started coming off from one side. When I looked at it closely, it seemed like the battery of the phone is swollen and the battery also stopped charging. I took the phone to the nearest nokia service center in Tilak Nagar. The person there told me that since swollen battery is considered as physical damage, the phone is no longer covered under the warranty. I told her that how can a swollen battery be considered a physical damage as it did not happen because of the phone dropping or anything else and it is dangerous as the battery could explode as well. She did not want to listen to me at all and said that this is a company policy.

My concern here is that if a battery swells up, how can this be considered as a physical damage and why should a customer be paying out of their pocket for it.