To update the credit card details for your iNewsletter subscription:
Go to Naavi Billing
Click Manage next to the account you'd like to update card details for
On the next page, click the pencil icon next to Payment Method: Credit Card
A popup window will appear with a form to enter the new card details
You can also choose to re-attempt payment on any unpaid invoices, instead of waiting the normal 2 - 3 days for an automated re-attempt.