How to change payment details of my order

Downloadable (Standalone) license - SWREG
In case your order is handled by SWREG, then you can use this link to take some actions like changing your credit card details, investigating why your order was not accepted etc. :

Hosted (SaaS) solution of Post Affiliate Pro/Network 
If you use our hosted (SaaS) solution of  Post Affiliate Pro (Network) then you can update your payment information directly in the merchant (network owner) panel in the My Account section.
Note: If you are not logged in PAP/PAN using https:// protocol software will ask you to use https:// protocol before you can continue with the update of billing details
If you visit the My Account (My Account > Overview) section and you see there a message like 
"Recently we have changed our payment method to more robust and safe solution. We need you to re-enter you billing and credit card information
just like you see in the image below
then first you have update the payment method. 
Simply click the "Update payment method" button or navigate to the My Account > Payment method section and there you can choose the desired payment method (Credit Card or PayPal):
Once you updated the payment method you also need to proceed to updating your billing information (that is supposed to be shown in the invoice) in the My Account > Billing info section:

That is it.