online booking

I booked a flight online on Thursday @1h25pm and I opted for the EFT payment system which payment has to be effected within 72hours. On Saturday, I went online to pay my booking around 2pm and my booking reference number was not being accepted by the system so I called SAA to find out if they were experiencing technical difficulties with their online payments. I gave him my reference number and he said my booking was no longer available and I had to redo the book inspite of the 72hours. I booked the flight at a higher fee but I was so disappointed by cheating customers to believe they can still pay within 72hours. What's the use of having a reference number if they wont honour the contracting terms