Credit Card and my Keychain

First follow the steps in the article iCloud: Remove credit cards from Apple Pay to remove credit card from iCloud.com

Then open keychain access through spotlight click on icloud in the keychain access side bar , search the card , right click on the card ( if in any case it is found ) and delete the item .

you give no clues as to what you have - on a mac you launch the Keychain access application in the utilities folder in your Applications folder to modify Keychain

LN