There is a lot going on behind the scenes with Apple Pay.

When you add your card to Apple Pay, you are not actually adding THAT card number to Apple Pay. Apple simply uses the card number and related info to engine the process or verifyzing with the card issuer that you are really you and that your account at the card issuer is valid.

Often there is an additional step where you must connect with the issuer and confirm/authorize the addition of Apple Pay to your account.

When all this is complete, the Apple Pay on your iPhone is linked to the account at the card issuer, and that linkage is quite separate from the card number on the plastic card you used to initiate the process.

Every time you use Apple Pay, the iPhone uses a unique one-time-use ‘number’ to authorize the purchase. Apple Pay Also coordinates with the card issuer for each payment, and when the transaction is complete there is no way for the retailer to ‘re-use’ the payment info to cause another payment to occur.

If the plastic card (number) needs to replaced, that does not affect Apple Pay since it does not ‘use‘ the same number that is on the plastic card. And since Apple Pay directly communicates with the card issuer via the Internet, Apple Pay is kept current with changes to your account.