In our system, the billing address will be automatically generated to the same as shipping address, if you want to change it, you can click “edit” at the checking out page ( this will only work at the first time checkout ).
If you paid already, then no need to change the billing address, as we'll just ship the order to the shipping address that you left on our site.
Therefore, it does not matter that if the billing address is different from the shipping address.