Gautrain

I travelled in November and my train card had funds. Got back today and I tried using my train card I'm told it has expired and I went to buy another one and asked for the money on the old card to be transferred because I had already calculated my trip and then I'm told the money in the old card has expired too. How can money expire? It was 7 mins before the last train left the airport and I was told there's nothing that can nbe done. I did not even have enough money with me . I am very unhappy about the service I got at O R Tambo Gautrain.