How do I change the e-mail address that receives Apple Pay notifications?
From the Apple Pay Support page:

Update your billing and contact information
Learn how to update your billing and shipping information for the cards that you use with Apple Pay.
iPhone or iPad

To change your billing information, go to Settings &gt; Wallet &amp; Apple
Pay, tap a card, then tap what you want to update.
To update your email address, phone number, and shipping address, go to Settings &gt;
Wallet &amp; Apple Pay, then choose what you want to update.