Very bad service from British Airwais

i went to the airport on 27 march to return to johannesburg but they would not let me and my two friends on the flight. they wanted us to pay again for the next flight out which was double the price. i did not get any assistance as we arrived 20 min late due to traffic. I did not even get some kind of refund or a call from this airline. the consultant the assisted us was so cold towards the whole situation