This has happened many times before and has been discussed in here before - although not for some time, I think.
As far as I recall (notice the deep caution!) the agent has to verify the destination. For example, whilst many people asking for a ticket to 'Sydney' would mean the big city in New South Wales, others might mean the town of Sydney in Nova Scotia.
If the agent did not notice that there was more than one Melbourne on the system, it is likely to be their fault. For example, Wikipedia lists 5 Melbournes is the USA alone
Melbourne (disambiguation) - Wikipedia, the free encyclopedia, so why did they not check which of THOSE five it was??? The link also mentions three Melbourne's in England and two in Canada. Since the New World, Oz and NZ were all populated by Europeans, it might have occurred to this travel agent that there is a good reason why a certain town was first called New Amsterdam and then renamed to New York.
