Unexpected Battery Replacement Costs for Xiaomi Robot Vacuum

I bought a Xiaomi robot vacuum from Media Markt, but it broke down before the warranty period was over. After I sent it in to be fixed, the service center told me that the battery problem wasn't covered by the warranty and asked for 2,750₺. It was never made clear to me when I bought the vacuum that battery problems would not be covered by the warranty. Someone I know had the same issue with their Roidmi Eve Plus robot vacuum, and the battery was replaced for free. I'm also asking for the same thing: the battery in my vacuum should be replaced under warranty, free of charge. I want this problem to be solved quickly so I can stop being so angry.