Your Mac will use the default card in your Wallet that's set up to work with Apple Pay. If you have multiple cards in your Wallet, you can easily change the default card your Mac uses by following the steps below.
Bear in mind, whichever card you choose as the default will become your preferred card for Mac App Store, Apple Music, and Apple services. Here's how it's done.
- Launch System Preferences from your Mac's Dock, from the Applications folder, or from the Apple menu bar ( -> System Preferences...).
- Click Wallet & Apple Pay.
- Select your preferred card from the Default Card pop-up menu at the bottom of the preference pane.