While using the Billing Utility, I accidentally double-charged someone's credit card for their monthly payment. I'm trying to adjust this by refunding half the gift, but whenever I try to close the the payment, a notification says that the payment schedule is out of balance. I've tried adjusting the payment schedule in several different ways, but it still tells me that it's out of balance, and won't let me refund until it's balanced. Is there any way to override or fix this payment schedule and complete the refund?