Be charged for their human error

our cruise booking was made with FlightCentre Benmore Gardens, however the surname for one of the children involved in the traveling was incorrect when I contacted FlightCentre I was told due to it being their human error I am still liable for a R600 charge to change the surname. how disgusting is that if I had to tell every client of mine that an error I caused they are liable to pay. even when I have sent them the email with the correct details sent to them. Very upset and angry even if they do get this sorted this is not how you treat customers