A refund is the act of returning money received previously for a products/services because the customer or client was disappointed for reasons such as faults in manufacturing or dissatisfaction with the service provided. 

Refund marketing is part of offering a guarantee to remove the risk of buying your product service.

Of course, when someone asks for a refund, give it to them promptly. 

And as long as you have their attention, ask why they are returning your product/service. Ask what you could be doing better.
Ask if there are any product/service you could be offering.

Asking questions builds rapport with the client.
They realize you care how they feel and many times will give you the opprotunity to sell them a better suited product/service.