I scheduled five nights, but only used four. I still got charged for five nights. How do I avoid this in the future?

I was charged $50 for the extra night that I didn't use. I came back a day early because I had someplace to be Saturday. If I had known I was going to be charged for a night I didn't use, I would have left my dogs until the following afternoon. I'm not really happy at this point because I can't seem to find a way to get any assistance.