If in any case  you need to refund your clients , you can do that from Paymes Panel :

Note : Refunds panel allows to Refund an order either in full or partial.

Open Your Paymes Account > Refunds Tab > then you will the options:
Either to Make a refund or view Previous refunds on Refund List .

To Make refund :
You'll find the list of your recent Transactions , so choose the desired Transaction you need to refund , then click on the (  X  ) sign to initiate the refund.

Then a message will appear so you can choose if you will make a partial or full refund.
Then Submit your refund request .