Online booking payment failure after 22:00

Bought a ticket and PAID online after 22:00 for a flight the following morning. The system processed payment and issues a booking confirmation, only to find out at the at check-in that the ticket was not issued. Consequently missed the flight. Asked SAA to get me on the next flight, they want me to pay 50% more expensive that the ticket they failed to process. WHAT ON EARTH IS THIS????? Can someone tell me what service is this?