If you knew that you were getting still bottled water then why didn't you check the price list before ordering it?
You are missing the point. I asked for and was expecting bottled water and I didn't mind paying €2.50 for a bottle. I did mind paying €2.50 for a glass of water (smaller measure than usual bottle) that apparently came from a 1 litre bottle that I didn't see get opened or left on my table. If you went into a pub and asked for a bottle of coke, would you be happy if they came over over a poured you a glass from a 2 litre plastic bottle that could have been open for hours and then charged the same.