I booked a hotel room in the Netherlands for 2 nights. The hotel was a pay-at-the-property hotel, and didn't need credit card details. Before I arrived I added an extra day over the phone. Upon arrival the owner told me that on the third night I would be getting a bigger room, but he didn't mention anything about the price.
On the day of the room change I asked the man and a woman at the front desk if there were any smaller rooms available in case someone had cancelled, but they told me I would not be getting charged extra for the extra night after checking the system.
It was strange but during checkout the next day, the woman at the front desk confirmed with me that I had stayed in a small room for 2 nights and an extra night in a big room and gave me the final bill, which I payed for.
One week later, I received an email with an invoice for the final night (150 Euros). I am unsure if I should be paying this extra bill after confirming my bill with 3 different employees throughout my stay and never being told about an extra bill until now.