How can I change/update my credit card on file?
If you'll go ahead to https://feedly.com/i/account/billing you'll be able to edit your credit card you have on file with us. If you don't see the button to edit the card, you've upgraded by PayPal and all the edits can be done directly in PayPal.
If you want to change the payment method from PayPal to credit card, the only way would be to cancel your current subscription, let it expire and upgrade again via credit card. If you don't want to wait, contact us and we'll be happy to help.