Breach of contract

On 14 August 2015 I traveled on SAExpress from Cape Town to East London on the 13h05 flight. The evening before, I had booked in and changed my seat to 10D. When I checked in my luggage on departure day, I was issued a boarding pass with 10D as my seat. Later when I went though the departure gate the female official told me seat 10D was \broken"- an outright lie I later observed as there was a passenger seated in 10D for the flight. My seat was changed to 4C. On the plane"