It is usually just the credit card terminal, or the screen you are using to scan groceries on. Most large chain convenience stores, grocery stores, ect. have a club card that you sign up for. They use these to get your info for targeted advertising and offer discounts. You can get the discounts and never sign up by just using the “Jenny” phone number. The number is registered all across the USA in different areas codes and on almost all store chains. These club or loyalty programs are different than Costco or Sam’s club memberships, which require paying a yearly fee to join and allow access to the store.