I don’t think it was a scam, the link that says cancel-pay.net links to a legit Apple website as well, at least I think. (The site is now down, but I think that may be down to the long time it has been since that message. But tbf, they did ask for credit card info, which I didn’t input) So I’m not really sure if it’s a scam or not. Given the verification code 3 years ago, I don’t think it’s a scam.
The situation right now is not that I have an unknown card in my Apple wallet, in fact there is nothing there, but I don’t understand why they messaged me saying my card has been added successfully when there’s no card anywhere.