Recently I tried to change the credit card used as a payment method in my Facebook Ads account. This may seem like a straightforward thing to do, but apparently it's not :).
So adding the card itself wasn't the problem, but when I tried to make it primary, so that facebook can charge it automatically this error appeared:
"This credit card can't be set as your account's primary payment method, because your account is set up to be billed after your ads have delivered. This setup can't be changed. Please try a different card or payment method."
From the little research I did on this topic, it seems that facebook accounts can be set to different charge methods, before delivery, after delivery etc, but this can't be changed after the account is created, you have to create new one...
The workaround I found was to delete all payment methods, but this isn't straightforward as well. When you try to delete your payment method this error appears:
"We need to verify your balance before removing your only payment method on file. Please go to "Manage Ads" and turn off your ads, then return here in 30 minutes to pay your balance and remove your payment method. If you don't want to turn off your ads, you can add a new payment method before removing this one."
which sounds reasonable thing to require. So you should stop all of your ads, wait 30 minutes, pay your balance and then remove the payment method.
After you remove all payment methods you can now add your new one. You still won't be able to make it primary, but I think when you have only one, facebook will charge it automatically. (I'm still on the process of verifying this).