If a subscription was accidentally signed up for on a website, then you will need to contact them for a refund. Apple is only able to provide refunds for purchases made with an in-app purchase. Apple Pay is simply the platform that allows you to make purchases securely without providing the other company your credit card number. If you use your physical credit card to make other purchases at retail locations, it is still susceptible to skimmers that will read your credit card number and those charges would appear in the Wallet app just like the others. It does not mean the charge was made with Apple Pay.
Review this support article to see if the charge originated from Apple. If it is not showing there, then you will need to deal with the company that did charge you or dispute the charge with the credit card company like you would with any other fraudulent charge.
If you don't recognize a charge - Apple Support
If the charge was made by an in-app purchase, then it will show as an Apple charge and you can request a refund here:
Request a refund for apps or content that you bought from Apple - Apple Support