You can update your payment method in your Subscription Settings or your Account Settings.
On iOS, your Account Settings show which payment method each subscription uses, and you can change it for each subscription there. On Android, adding a card in Account Settings doesn't change the payment method on your subscription, so use your Subscription Settings instead.
How do I change which card my subscriptions use on iOS?
Tap the 3-bar menu, then tap My account
Tap Payment
You'll see each payment method at the top, with the subscriptions that use it listed underneath
Tap Change next to a subscription to pick a different payment method for it
You can also add a new card from this screen.
How do I update my subscription's payment method on iOS from the subscription?
Open your active subscription and tap the Settings (gear icon) in the upper right corner
Tap Payment
Tap Add a card and enter your new payment details, or tap an existing payment method to update it
Tap Done
How do I update my subscription's payment method on Android?
Tap your active subscription
Tap the Settings (gear icon) in the top right corner
Tap Payment
Tap + Add card
Enter your card information and tap Add a payment method
How do I add a payment method to my account on Android?
Tap the Settings (gear icon) in the top right corner, then tap Payment. Tap Add a card, enter your card information, and tap Add a payment method. This card won't be used for your subscription unless you also update it in your Subscription Settings.
Watch how it works
Update your subscription's payment method on iOS
Update your subscription's payment method on Android
Update payment in Account Settings on Android
Using the website? See How do I update my subscription's payment method on the web?