I looked at both your current listings and your completed listings and they all either say that you post worldwide where there is a postage amount, or 'will post to Australia' and to ask seller for a postage quote. Nowhere does it say you don't post overseas.
You need to go into your settings and block all overseas countries if you only want to sell to your own country. Otherwise, you are going to keep getting overseas buyers who think they are legitimately able to buy your items.
You can't just cancel a transaction post sale because you decide you don't post to that country any more, when your listings say you post worldwide with no excluded countries. It's going to make for one very unhappy buyer, who will more than like give you a negative and trash your stars.
Now that he has rejected your cancellation request, you have 2 options. You can send him the book, or you can lose your FVF's. If you decide not to send, don't be surprised if he opens an item not received case against you, which will add another defect to your account.
