Cancelling of booking

we purchased 2 tickets to Durban which amounted to R5000, a week before the flight we needed to cancel as there were some problems unfortunately we were told we cannot cancel so we changed the ticket dates passenger details that now came to R6500, however, we had an accident and my dad fell and had a very bad head injury and could not travel i tried cancelling and was told we cannot cancel, how is that possible that you cannot cancel a ticket, i feel it is ridiculous that it can not be cancelled and this was a genuine reason because we paid alot of money and had to lose that, i will never fly Safair again i would rather pay more with another airline then fly Safair, pathetic service.