I think Apple Pay is gaining in popularity, more and more people are using it. I use it from time to time myself. An Apple Pay account is set to a Default Credit Card. From time to time you may wish to change the Default Credit Card in your Apple Pay account just like I had to do recently. Here is how you do that. This assumes you have more than one verified card in the Account.
Apple Pay Card
Changing the Default Credit Card in Apple Pay in iOS is really easy. You start by going into the Settings area. Scroll down and tap Wallet & Apple Pay:
On the next screen you will see your available cards listed:
Scroll down and Tap on Default Card:
Now all you have to do is Tap on the card to choose it as your Default:
That will be your Default Apple Pay card going forward.
If you are an Apple Pay user, it is easy to change the Default Credit Card used for that service.