There has been an uptick in credit card fraud related to Switch owners in recent weeks. Numerous people have been contacting Nintendo to let them know their credit card information may have been tampered with. Nintendo has been keeping an eye on the situation, and shared a statement on the matter.
Nintendo wants customers to know that they can enable two-step verification to keep their credit card data safer. This is a standard practice used by numerous companies nowadays, and should do a lot to prevent bad actors from gaining access to your credit card information and more.
Obviously, if you are having these issues or are worried about something happening, you can also change your password to something more secure. Avoid using the same password for multiple accounts, and use something that combines letters, numbers, and symbols.