Not willing to Help

I pre-booked tickets for me and my wife to watch Jurassic World at Cape Gate for Saturday 13 June 14:30. I did this way in advance. Now we unfortunately learned that she needs to go to hospital the weekend and will no longer be able to make it. We contacted Ster-Kinekor to hear if we can move it to a later date. To this they rep**** that their System does not allow movements, but I can cancel and then rebook for another date. But to this they also informed me that I will no longer be able to get a discount on the second booking as our cards was already used. As this is a 3d IMAX movie the difference is quite huge. I then asked if I could cancel one of the seats to which they rep**** that once again their system does not allow them to cancel part of the booking and the whole booking needs to be cancelled. I just feel in is unfair as I still want to watch the movie. Just at another time. Ster-Kinekor will not loose out on any money. I do understand that I should be penalized for an unforeseen circumstance. If it was for the fun of it I would have understood,