How do I update my Protect Subscription billing information?

For Apple App for iOS (iPhone, iPad):

You may update your payment method on your iPhone or iPad.

1. Open the Settings app.
2. Tap your Name.
3. Tap Payment & Shipping.
4. You might be asked to sign in with your Apple ID.
5. Tap Add Payment Method, enter the new payment method, then tap Done.
6. Tap Edit.
7. Tap the red Delete button next to the old payment method, then tap Delete.

For Google Play for Android: 

To change or update the payment method used:

1. Open the Google Play app .
2. At the top right, tap the profile icon.
3. Tap Payments & subscriptions Subscriptions.
4. Select the subscription you want to update.
5. Tap Manage Update.
6. Follow the instructions to update your payment method.