Don't trust these guys

I booked a flight in January to visit my mother on her birthday in April. My mother fell ill and is now in Pretoria. I can't fly down to Port Elizabeth now. I spoke to the travel agent and the airline. Both of them refuse to refund me for cancelling a flight three weeks before the flight. I can understand if I am giving them an unreasonably short time to resell my ticket, but surely 3 weeks is enough time!? I never received any communication from them saying that the flight was non-refundable. Not on any communication was this printed. How can this be considered a reasonable or ethical business practise?