Unable to use last 44cents of a US purchased iTunes card in Australia and therefor can't use our account for anything else! Please help.

We purchased an itunes card in the US and were able to use all but 44cents of it. We are now back in Australia and on trying to change the account back we cannot use the last 44cents for some reason and due to that, we cannot access anything on our account as we cannot change it back to our Australian account. Any help would be much appreciated.