Product Return Merchandise Authorization(RMA) makes entire Product Return Process very easy to manage. You can grab RMA extension for your Magento or Opencart Store which will let your customers to opt either for Refund or Product Exchange in case they receives any damaged product. Get RMA Extension for Magento here - http://goo.gl/A3p4xB and Opencart here - http://goo.gl/8wELSa