Force Currency on Checkout

Hi There, need your help, please.

The site has 4 checkout currencies, USD, ZAR, EURO, GBP. Anything that is not ZAR checkouts out with PAYPAL CHECKOUT (WOOCOMMERCE)

I need to force all the remainder of the countries like AUSTRALIA to checkout with the USD currency amount. Important to note, hard prices are set for each of the 4 currencies per product.

Wordpress backend: WooCommerce Multi Currency Settings -> Location, I have tried to add Australia to the USD currency.

However, front end does not force the change. On checkout page, if you change the billing country from South Africa to Australia, you will see the currency does not change. The amount remains in RANDS (ZAR).

Please can you help sort this out. This is a live site, there are shoppers wanting to Purchase, one from AUSTRALIA, the other from POLAND.

Also, important to note, POLAND is added to the EUR currency, and front end checkout does not change to EUR for POLAND.