Kampgrounds Of America [KOA] review: early check in fee

My husband and I drove 16 hours straight through to The KOA. We arrived a few hours early. Our site was open and the campground less than half full.
When we went to check in they first told us we had no reservation. I had to pull it up on my phone to show that we did. Then they charged us extra but did not tell me. When I realized it I showed her the original reservation and asked why the extra charge. They said it was because we were checking in early. I said why didn't you tell me that? I got a halfhearted sorry and nothing else.
This is not good business practice. Just tell people if you're gonna charge them for every little thing. But to just charge and not say anything shows lack of care or deceit.