I created a customer invoice once a reservation is made. The customer pays the deposit online as part of making the reservation. I open the invoice and receive the payment of the deposit. Once the customer pays the remainder after services rendered, I go to receive payment to add the balance. However, when I try to enter the new (additional) amount, I get a warning saying that I am changing the payment amount and do I want to continue. I am just trying to receive the additional payment. What am I doing wrong?