Sharks in airlines

BA is the worst airline I have ever been with. These people's system did not allow me to book in advance. When I got to King Shaka International Airport to explain the situation they told me that I was to book another flight. How is this ethical. I got there in time for the flight but I need to pay for another flight. This needs to be taken even higher. This is the second time they do this to me and Im supposed to continue taking it. Bulls#=?t they are sharks. Mnxx