I was renting a surfboard here and returned it one...

I was renting a surfboard here and returned it one day earlier than I told them I would. Well, it turned out they charged me money up front for the three days and would not give me refund even though I returned the board earlier. I have been renting surfboards on Oahu for many years and many times I had to return the board earlier for different reasons and I was always charged for the number of days I actually had the board, not for the number of days "I was going to". Of course nobody told me about such "rules" in advance, I would never sign up for that. By the way even with car rental companies if you return a car earlier they will charge you only for the number of days you actually had the car, its a standard rental practice, so I did not even expect this could happen to me. If you rent a board in this place then you have to watch your back and be extra careful about what you are signing...