Bad service

I book 2 return tickets from cape town to Johannesburg in November last year for R3500 including the option to chance .(fkexable tickets).My mother got hospitalized in Pretoria on the 1 January. We try to change the booking to a earlier date ,but couldn't got hold of travelstart or Mongolia due to the public holiday. We book new tickets.I was told by one of their agents that the tickets is valid for 6 months. Today I want to change the dates and were told that I must pay a penalty of R3300.It is more expensive to change dates as to buy new one.what now.We cant fly next week due to my mother's medical condition. NEED HELP PLEASE. Travelstart or mango don't want to help.Next step is to get hold of ombudsman