Incorrect CC's on Constituent Record

Hi all,

I've noticed pattern of incorrect credit cards on customer's constituent records and I am wondering why this is. For example, when I go to process an order, enter the credit card type in the payment screen and select the "accounts" screen, there have been 1-2 credit cards (with valid expiration dates) that patrons have never heard of. As this is a repeated occurrence, I do not think it's simply a matter of patrons with canceled cc's, new cc #'s ect.

Any insight would be helpful, thanks. 

Michelle