Cancellation due to medical reasons

We had booked and fully paid for a 7 night stay at the Fairmont Zimbali resort for the first week of January 2016. Unfortunately, we had to cancel for medical reasons - and provided a doctors letter a week before the booking to prove this. The resort was very unresponsive and eventually rep**** that they would not refund us nor let us change the date of our booking. Quite unbelievable given that the request was due to medical reasons and accompanied by a doctors letter! Not even sure it's legal. I am totally shocked by the resort's response and will certainly never be going there ever again.