This is a lesson learned. Always read what you are signing/clicking.

Credit card issuers (banks) don't decline charges, rather they can be disputed. You can always try, but Norwegian will simply respond that you were advised of and agreed to the charge. I would also be very careful of doing this with the ticket pending travel as, if granted, it might cause Norwegian to simply cancel the ticket as not fully paid (likely) or hold it for an add/collect at check-in (very unlikely).