I'd like to verify some information. Are you trying to record a refund for the item or service.returned by your customer? If so, you can use the refund receipt transaction. Note: Make sure to check if there's no credit note entered to avoid a double refund.
Here are the steps:
Go to + New > Refund receipt or Give refund.
From the Customer ▼ drop-down, select the customer you want to refund.
Choose the bank from the Refund From ▼ drop-down menu, and add all products or services the customer returned in the Product or service column.