I will never fly with mango again

I arrived for my flight early today and have asked for an earlier flight to Cape Town. Mango has asked to charge R1800 extra in order to change my flight, I can understand a R450 extra fee but double my flights cost is pushing it. My friend that was flying with BA were so accommodating that they have put her on the next flight home and at no cost. Service is very disappointing as a customer you would expect the staff to go out of their way.