Flysafair is an opportunist airline

I bought flights when it was kids free pay airport taxes only for Oct school holidays and I got a miscarriage at 21 weeks so I then opted to change the date for my flights but the amount was too much, it was over R8000.00 so flysafair system did not take me back to my original flights after my payment to the new date I had chosen did not go through. When I call now I'm told my previous flight is full for 7 people. I ask if there's no timeframe for their system to take me back to my original flights after payment failed and their response is it should take an hour if it is a new booking but with making changes to an existing booking it doesn't . Flysafair saw an opportunity to sell at a hight price all 7 seats I booked since I booked when the was the so called special.