Penalized R550 for 10min

This morning we had booked a child on a mango flight , en- route the person dropping the child had car trouble , the flight was for 6:20am so we tried to contact them to let them know we would be a few minutes late but all listed numbers are only tended to from 7am , we then contacted Acsa who put us through to them , boarding had not yet closed but the lady said that there would not be a possibility to put him on the same flight if we were late but could confirm him on the next flight with a penalty payable , they arrived at the airport 10 min after check in closed and without any bags to check in but they refused to allow check in and charg d a penalty of R550 and still said they were doing us a favour at that price. They could have confirmed him on the flight when I called as check in was not closed but the penalty was more important then assisting us , life happens to everyone and they just profit off people's mishaps yet I once was on a flight with them that was delayed for 3 hours and only after contacting them and explaining how they had costed me an extra days accommodation and a flight change due to their delay did they give me a mango voucher for R250 ...... Fair?