Pixpa uses Stripe for credit card processing. Your credit card data is stored securely with Stripe. Pixpa does not have access to the credit card data.
Stripe automatically charges your credit card for the Pixpa recurring subscription.
If your saved credit card expires, Stripe automatically updates your new credit card details in its system so that you do not have to go through the hassle of updating your card manually and your subscription stays active. See the Stripe article on this.
The saved card only stays working as long as the credit account stays open. You will not be billed after you cancel your subscription or close your credit card account.
If you want to add any other card, you can manage it from Customer Portal. Click here to know more.