Xiaomi Device Is Kept Out Of Warranty For A Sensor Rusting Issue

my device broke down and luckily it was still under warranty, I sent it to the authorized service center, EXACT Service. I was so surprised when they said that even though I didn't do anything wrong, the sensor got all rusty and they wouldn't fix it for free. They asked me to pay a crazy amount of 3640 to fix the issue, so ridiculous that they won't cover my device just because of some sensor issue that I couldn't even mess with if I tried.  the service center must fix my device for free like they promised in the warranty. EXACT Service is trying to charge such a ridiculous amount for a manufacturing mistake? It's outrageous! It's their job as the authorized service center to take care of any problems during the warranty period. They can't just randomly deny a warranty for something that's my your fault.