billing address locked to US only

I have tried to change the default billing country to Australia and follow all the instruction of how to do it and also click "save" after the change as well.  However when i have try a test on my actual website, somehow the country still only locked to US.   Please help

Have you added Australia as a shipping option in Commerce > Shipping?

Shipping Settings lets you control what shipping options are available to customers. Countries not served by any of your shipping options will not be accepted at checkout.