You can update your payment information within your iPhone app by following the directions here:
Tap Settings on the bottom right of the screen. Tap Payment Methods in the list. There are several payment methods allowed within the Parkmobile system but you must choose one that is accepted by your parking authority. You would not want to try to use PayPal, for example, in an area that doesn’t accept PayPal as a payment method. So only choose to add the Parkmobile Wallet or PayPal if you are certain that payment method is accepted in your area. To view a list of which areas accept these payment methods you can view the links on that page or locate this information in our Help Center.
Near the bottom of the page you’ll see the Credit Card section and the credit card information you’ve previously added to your account. Tap the appropriate button at the bottom of the page. To update your Primary Credit Card or Secondary Card (if applicable) just tap the card details shown. The Update Credit Card page will appear with blank fields (your information is saved in your account but for security purposes will NEVER appear in your app.) Enter your credit card number, expiration date, card security code, and your card’s billing zip code. Tap the Save button at the top right of the screen. If you have a Secondary card and you’d like to make it your Primary instead you can tap the ‘Swap Primary and Secondary’ button and it will flip the two cards so that your Secondary card becomes your Primary, and vice versa. As explained at the bottom of the Payment Methods page, Your secondary credit card will be used in the event that your payment is declined or your primary card type is not accepted in the zone in which you are trying to park. A primary card cannot be deleted. To delete a Secondary card, swipe left across the card details and a Delete button will appear. Tap the Delete button to delete the credit card information from your account.