I get a warning when enter my client's credit card into my software- it keeps saying "invalid card number". On investigation it turns out that the number is weird, in that it does not satisfy the Luhn Algorithm.
(For those of you who don't know what the Luhn Algorithm is, the number on your credit card is not just random digits, it actually has a particular property, where if you add and multiple various digits together you should get a total divisible by 10. If you don't you can tell the card is invalid. Explanation here.)
Should I try to override this warning? My client swears that their bank says the card is valid.
Should I try to contact their bank on their behalf?