Ok this is kinda freaky and gross, but this is supposed to be helpful!!!
My parents had an animal in their attic. It kept walking around and I would hear it when I went to their house too. The exterminator set traps a few times and the animal always got out, but kept coming back.
Long story short, it was a possum and it finally DIED in their attic. The stench was SO horrible I can not even explain it. It was the worst smell in the world.
Call tomorrow and be VERY persistent with them to look into this and catch the animal. And then you should have someone out to your house to cover up the holes that are allowing the animal in. Some laundry something or other wasn't sealed properly at my parents house.
Best of luck, but take care of this now!!!!!