Owing Money On Top Of Security Deposit, But There Was A Pipe Burst 1 Month Before Move Out

Location: Madison Wi.

My former apartment that I lived in for 3 years sent me a letter that I owe them $850 on top of my security deposit. The letter says this is because of a pet odor they had to replace the carpet ( I had 2 cats). How do I dispute this charge that it is mold due to the flood not the cats?

The letter they sent me shows handwritten math that the apartment should have been able to get an additional 3 years out of the carpet therefore I need to pay for the difference. I paid pet rent and a pet security deposit. I moved out in the end of August, but on July 4th a water pipe in the communal hallway celling burst flooding the entryway of mine and several other units. The fire department came and I watched them pump water out of the front door there was so much water. My apartment management company did not replace the carpet in the hallway or the entryway of my apartment. They just put a couple industrial fans in the hallway and in the units that were affected for ~1 week. So I believe they are trying to get me to pay for their negligence. I have a voice recording of the walk-through with the apartment manger disputing this item on the check out-list

There is no email address to respond to them - just a phone number to arrange installments, or an address to send the check.

(The cats are loved and have 2 litter boxes one of them being an automatic litterbox, I have never had another apartment say this to me, nor did any of my friends, say anything.)