Booking.com is the most unreliable service provider

My wife booked a property in August, we settled the booking in full in November and today we received communication that our booking has been cancelled because Booking.com double booked the property. We have 14 days to go before our holiday and we don’t have any accommodation. We cannot book alternative accommodation because Booking.com takes between 7 to 12 working days to process a refund, even though they are the ones who cancelled on us. This is completely unacceptable.