Weird text message about apple oay

What exactly did the text say? and who does it indicate it's from? Apple or a credit card company? If from a credit card company, is it from a company you have a card with? If so, I think I would call the credit card company and review with them.

I've added several cards to Apple Pay and the only text interaction I've had is when the credit card company sends a verification code during the process of adding the card. (and only a couple of them did that)

If you are concerned, you could consider changing your Apple ID password.

And while you're at it, make sure 2 factor authentication is turned on.

Change your Apple ID password - Apple Support

Two-factor authentication for Apple ID - Apple Support

I don't even think a compromised Apple ID leads to someone being able to add one of your credit cards though. Especially if you've never set up Apple Pay before. I just checked on my iPad, that's also signed in with my Apple ID. adding a card to Apple Pay is a little easier because it knows which cards I have on my iPhone.. but in adding it, I still needed the physical card to get the 3 digit code on the back.

So it could just be a phishing/scam text?

That is a relatively new scam message. Do not interact with the message or the sender.