A Hotel Booking Problem

Dear Customer Service Team, I booked a double room at your hotel for 14 and 15 November. My confirmation email says the reservation includes breakfast. However, when I arrived yesterday, the receptionist told me there was no reservation under my name. I showed her the confirmation number, but she could not find it in the system. She offered me a single room at a higher price. I accepted it because it was late, but the room was smaller than the one I paid for. Could you please explain what happened and refund the difference? I have attached my booking confirmation and receipt. I look forward to your reply. Kind regards, Daniel Torres