Your Wordpress Theme should provide the following functions:
- Ability to add a Billing/ Shipping address
- Ability to update shipping destination, City, State & Post Code
Whilst on the checkout page, you have entered a Post Code, if you select a different Post Code the shipping cost will be updated.
You will notice a spinning icon which represents that your Wordpress Theme has the ability to refresh the shipping information.
If you cannot update the shipping cost based on the Post Code you have entered on the checkout page, your Wordpress Theme does not meet the Wordpress eCommerce Standards, for providing specific functions for shipping.
You may want to enable a Standard Wordpress Theme ( Twenty Eleven,Twenty Twelve, Twenty Thirteen or Twenty Fourteen. ) and go through the checkout process, changing your shipping destinations.
The shipping pricing will update/ change when you change the shipping address.
You will need to reach out to your Theme developer.