HeatSpring subscribers can easily update the credit card number on file for their Plus or Pro plan. Just log into your account at https://heatspring.com/signin then click "My Account" at the top right. Then, navigate to your subscription page by clicking "Billing" located in the left-side menu. There, you can update your card or cancel your subscription under the "Subscriptions" section on the "Billing" page.
Credit card transactions are processed securely with Stripe. All credit card data is passed directly to Stripe and stored in their vault and HeatSpring never stores nor sees credit card numbers.
Updating your credit card through your HeatSpring account will update the card on file in the Stripe vault to be used for the monthly or yearly subscription charges. HeatSpring will also send out notification emails if a charge to your card fails with a quick link to update the card from the email. Updating your card through either method is acceptable.