Occasionally in the Take Order screen as you're entering an order, you will attempt to enter a customer's information and be met with a pop-up like this:

This pop-up is intended to warn you if you are attempting to create a duplicate record of an existing customer, and will let you choose to either edit the record or enter a new customer account under the same name.

If you click the name of the existing account, this will allow you to allow you to make changes to the account which will be saved when the order is completed.

If you click "No, create a new account with the name [XYZ]," this will clear the customer information you had previously entered and let you input a new customer account that will be saved when the order is completed.