Digits

 Barb had to rush to pay for a pickleball tournament and she looked up her credit card number in her records instead of getting up and getting her card. The payment wouldn't go through even though she was very careful putting in the numbers and checking them over and over. Then she found her real card and realized since it was a fairly new card the three digits on the back of the card were changed and she hadn't written the new number in her records.