I've booked a place for one night at Royal Stina hotel in Maboneng, All was confirmed and PIN was sent but when I got there that day I was told the place is fully booked while I booked days before

I've booked a place for one night at Royal Stina hotel in Maboneng, All was confirmed and PIN was sent but when I got there that day I was told the place is fully booked while I booked days before. I had to run around looking for the place to sleep at night, I don't recommend this app and the hotel how can they double book the place and took my money and I'm also told I must pay the fee whilst it's not my fault. I was not the only one booked at the same space, so it was tripped booked by bookings.com.i feel they ****med me I want my refund.