NOTE: This article only applies to purchases made on or after 7-July-2016. If you are concerned with a purchase made before 7-July-2016, follow the directions here for changing the credit card on file. What is special about 7-July-2016? That is the date on which Intuiface changed its payment processor from 2Checkout to Stripe.
To update the credit card information on file for subscription or MSU entitlement renewal, go to the My Payment Cards page on the My Intuiface website. Select the appropriate credit card in the drop down list on the left - i.e. select the card used for the purchase in question - then click the "Update this card" button on the right. Finally, follow the directions.