Unauthorised access to my Apple ID for Apple Pay activation

1. This is a user to user forum, you are not addressing Apple here directly. As users, much like yourself, we did not and cannot notice anything in relation to your account.
2. Any such messages are always, always scams. Apple will never send such messages for any reason whatsoever, and your Apple Account is not used when using Apple Pay at all. Apple Pay requires biometric authentication, so unless someone has access to your iPhone or Apple Watch they cannot use Apple Pay as if they were you at all.
3. You can forward the messages to reportphishing@apple.com, ignore them, and delete them.
   1. click here ➜ Recognize and avoid social engineering schemes including phishing messages, phony support calls, and other scams - Apple Support

Yes, it is a scam and seen by many people. No one is trying to access your Apple ID. All you need to do is delete and enjoy your day, just like you would do with all the other junk messages you likely also receive.