If your customers decide to pay using a different payment method than previously arranged, you can change the payment option. For instance, instead of payment against an invoice, your customer decides to use Paypal. Here is how you can do it:
Open the order.
Click on the pencil to change the payment method.
You can only change the payment method for orders which have not yet been paid or partially paid.
You can choose the preferred payment method and confirm the change by clicking the green "Change payment method" button.