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Well, all they do is switch the names of the accounts. I'm not sure what Tourism Australia's username was before, but Twitter switched their username over to australia and that way Tourism Australia's followers and tweets transferred over automatically. And since Tourism Australia's username is now australia, which was previously your username, then that means your account had to be moved to a new username which in this case turns out to be Australia1_. Unfortunately I don't think there's much you can do about it at this point.

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