Apple Pay: change billing address for Apple Pay added card
First listed response to this issue is "go into card to change" but does not specify *where* to "go in".
More precisely, the procedure is:
1 Launch Wallet on an iOS device.
2 Select the desired card for billing address change.
3 Tap the "three dot" option icon, screen upper right on iPhone.
4 Sweep up to locate the BILLING ADDRESS option.
5 Tap the right pointing arrow (greater than symbol) that links to the SELECT A BILLING ADDRESS page.
6 Select an existing address, or tap "Enter New Billing Address" to provide one not already listed.
7 Tap left pointing arrows at upper screen left to get back to the "Done" option within Wallet. Tap "Done".
8 Completed.
iPhone 11 Pro Max, iOS 13