Booking.com disgusting service ever

I booked a twin room in Sydney for myself and a friend visiting from UK. At the point after clicking on twin room there wasn't a warning to say that twin room wasn't guaranteed. When got to hotel found didn't have a twin room. Hotel said should have booked with them directly. Rang Booking.com - they said room cofiguration not guaranteed and I should have known as this information was on website!! obviously if this was clear at time of booking I would have gone elsewhere. When I rang, there was no attempt by Booking.com to help or compensate or refund. Attitude was too bad I should have known room configuration was not guaranteed!!!