Hotel charging for pets.. we have none

We are in a hotel for work. The first week we stayed on the bottom floor, but checked out hoping to go to another town. That didn't happen so we checked back in a few hours later and we are now on the second floor. I looked at the bank account and they charged $50, that we don't have. We are on a very tight budget. So my husband went down and they said there were pets in the previous room so there's a charge. He told them we don't have pets. They said one of the towels and a blanket smelled like pet urine. My daughter peed through her diaper one night onto the blanket but it was literally a SMALL spot. I told them I would wash them, they said it's okay. My husband works in a field and come home smelling gross. Maybe after his shower he didn't clean good enough and the towel smelled like him, idk. There are no stains or anything on them. They also said the room was dirty. It wasn't. I even took disinfectant wipes and scrubbed everything before checking out. There were crumbs on the floor but that's it. They can sweep that up.

They are still saying that we have to pay it. We even told them they can check our current room for pets. Are they allowed to charge for that when we don't have it?