We are using an Acumatica certified CC company, not sure if this applies to other integrations. We can add a credit card to an existing account, up front during an order, but NOT during invoicing.
We have many orders called in and when the customer picks up, they give us a card. The card can change based on who is picking up. Or they give us a completely new card.
When shopping online or in a retail store, choosing a credit card is the last step. Not sure why it has to be entered first in Acumatica.