Hostal Fernando in Barcelona

I paid the price of "Economy Twin Room, 2 Twin Beds" for one person to stay, but I got a "Single Room". When I checked with the staff, I was told in their system I booked a "Single Room", but when I showed them the picture of "Economy Twin Room, 2 Twin Beds" of my reservation, I was told they based on the room type. I disagree, I told them when I saw “Single room”, I thought it might mean single person to stay in the hotel, as a traveller, I didn’t care too much what’s a room is called, I only pay attention if the picture of the room was I looking for. Then the staff and I tried to book again to see the outcome from booking Single room vs Twin room. We found if we book a "Single Room" it would show the picture of "Single Room" and if we book "Economy Twin Room, 2 Twin Beds", and it will show “"Economy Twin Room, 2 Twin Beds". Right now, my case is I paid "Economy Twin Room, 2 Twin Beds" with the picture of "Economy Twin Room, 2 Twin Beds", but it showed “Single room” in the detail. I think something might be wrong with system, but I am not the person to pay the error. I need get the different between the Single and Economy Twin.