We are stuck JHB Airport

We are stuck at JHB airport. We paid for two tickets from Johannesburg to Frankfurt and then onto Malta as well at the return. The day before our flight we made a change to the second leg of our journey. We arrived at the airport to board in plenty of time and for some reason the call centre could not take the payment off our debit card. We were not notified and when we arrived to check it took about an hour to find out what the problem was and we missed our flight. What is more frustrating is that we had already paid for a full return flight and Lufthansa had messed up the change. We are now being told we have to pay R9000 to get onto the flight tomorrow. We are having to pay a penalty and miss out on a day of our overseas holiday thanks to Lufthansa's incompetence. What's worse is that when we asked why we weren't helped efficiently by the man at the check in assisting with our problem he mentioned he had the other customer he was attending to who got in the plane and was upgraded was a special customer. We are now waiting for someone to help & stuck at JHB. We don't even live in JHB so will have to pay for accommodation here as well!! This is the most shocking service ever!