Not So Free Cancellation at booking.com

I made a holiday reservation at a resort in Mozambique through the booking.com web page. They advertised this resort, and accepted and confirmed my reservation. The advert clearly states "Free Cancellation" on this web page. Three weeks after the reservation was confirmed the resort contacted me an advised that should I want to retain this reservation then I am obliged to pay a 50% deposit to them. Which I then did. Subsequently we have run into an emergency and have had to cancel this reservation. I advised the resort accordingly, and requested that they refund my deposit. This happened five months ahead of due travel date. I was advised by the resort that they have already spent the deposit, and as it is now low season that they will not be able to refund me before the end of the year. The booking.com "free cancellation" policy is not what it states to be.