Nice Hotel, but Not happy...

Liked: Accommodation, location, food and facilities were good.
Disliked: I am 66 years old. I inadvertently booked the room twice, due to Booking.com crashing whilst I was paying for the reservation.On arrival at the hotel (with my older brother) I was surprised that I had two rooms booked. As it was 3 months since booking I assumed that I must have booked two singles for us. When we got to the room, I realised it was two twin room and therefore went back to reception to cancel the second room.Initially the desk receptionist was about to refund some of the cost (excluding the Booking.com fee). Then his boss came out and she flatly refused to compensate me for the error. Hence we had to pay full price for two twin rooms.She was quite rude about it and unable to understand that as a pensioner, this extra £330 would have a significant impact on my spending power for the rest of our holiday. Her argument was that Booking.com had already been paid. Booking.com get a reservation fee - not the full accommodation charge.