Unforgiving

I booked a flight to Port Elizabeth, paid for it in full. The function has now been moved to East London, but Mango do not fly to East London. I tried to cancel this transaction and get my money back but have been told I will loose all the money. How fair is this - I never cancelled the function, so I get shafted by Mango. I understand if it was the day before - but this flight book is booked for the 24th July, all they can do is cancel the booking. Mango you suck!!!!