If the billing occurs through Paypal, one can simply change the cards that are used for billing within Paypal.
If the billing is made by credit card through our website, one can change the card associated with the account by logging in http://autismparentingmagazine.com/login/ and going to the menu item that says "Billing Information."
If the billing occurs through Apple's Appstore, one can simply change the cards that are used for billing within Apple's Appstore.
If the billing occurs through Google Play, one can simply change the cards that are used for billing within Google Play.