Refund form Booking.com and 326 Long Avenue Guest House

I made a resevation through Booking.com and paid for one night, when i got there they refused to allow me in say that they are fully booked and i should call Booking.com for a full refund. At 10pm in the evening, where am i going to go and the inconveince due to the guest house cancelling my resevation. I eventully got through to Booking.com the next day and they took down my complain and said they will have to confirm with the guest house if they did accommodate me for the night, they cannot get hold of the owner for the guest house and said they cannot do anything or any refund until the owner confirms that i did not stay for the night.