I sent my HTC One in for repair because the camera...

I sent my HTC One in for repair because the camera was malfunctioning (dark photos were pink) but otherwise the phone was fully operational. It was under warranty, still under a year old. A week after I shipped it in, they called me and advised me that it will cost $295 (plus tax) to fix. I said I don't understand, why isn't it covered under warranty? And they told me they found corrosion inside the phone. My phone has never been dropped or been in water. Maybe it got moisture inside it, but I thought phones are designed to handle that. Anyways I declined, they charged me a $35 (plus tax) Analysis fee and shipped it back to me using FedEx the next day. Not happy, with them or with HTC.