Kulula airlines - terrible service

My mum was booked for a flight from Durban to Johannesburg on the 12 January 2020, unfortunately she fell ill with chest pains. I phoned kulula 3 hrs before the flight and they refused to change the passengers name or refund me. They said the only thing I could do was change the date which would cost me R400 and also I wil need to pay whatever differences thats due. The ticket cost R700 and to just Chang date was gona cost me another R700. That is terrible service. My mum is 75 years and has a lump on her lungs so I could take a chance and let her board that flight.