From a
post by Whackbag:Add another credit card to your acct (doesn't need to be legit) any card generator will do for this purpose, then when you put the address in for the "new card" use one from the region you need the book from.
This will allow you to spend your credit on it... after you've got it just remove the "fake" card and make the original card stored on your acct the default & everything will be back as it was.
Audible only checks for a legit card number when making a new acct... Once you have a legit acct it will accept fake numbers again... you cant use them to "get or buy" anything but this works to change the address associated with your acct allowing you to spend credits on books from other regions.