How To Refund Charges
Login to your account at authorize.net and in the left-hand sidebar click Unsettled Transactions. If you see the transaction here, click Void.
If the transaction has already been settled (funds deposited into your bank account), then click Search By Batch, find the transaction, then you should see a link to Refund.
Login to your PayPal account, click on History, search for the transaction, and you should see a Issue Refund button next to it.
For more information or if you have any questions please email firstname.lastname@example.org