To refund money back to the user, follow these instructions instead.
From the left navigation menu, click Business Tools > Billing Manager.
Search for and click on the account to manage.
Click + Credit.
Enter the "Title" and the "Amount", and choose the charge category/categories.
If desired, click Restrict Credit to Charge Category to ensure that the credit can only be applied to the charge categories selected.
When finished, click Create Credit.