Hi theSteevo,
Welcome to the Apple Support Communities! We understand you're having issues with removing an old card from Apple Pay, and we'd be happy to get you pointed in the right direction for help.
To get started, by chance is this card still showing up as the default card on your iPhone? If unsure, check out the steps listed in the following resource under "Change your default card": Manage the cards that you use with Apple Pay - Apple Support
If the card doesn't appear in the Wallet app or in the Wallet & Apple Pay settings on your iPhone, then we would recommend reaching out to Apple Support directly from this link here: Get Support - Apple
From that link you'll want to choose Music, Apps & Services > Apple Pay > Bank Cards & Wallet. From there choose 'The topic is not listed', provide a short description of your issue, and you should see a few options to reach out, depending on your location.
We hope that's able to help.
Have a great day!