Refuse to refund: Faulty hard drive purchased

We bought an external hard drive as a birthday gift to my husband's mother in June 2015, the hard drive came with a 2 year warranty. We have taken it back twice already, due to the fact that it simply stops working and freezes completely. It has been tested by the manufacturers twice and the manager of Computer Mania claims that he tested it in the shop for 24 hours as well, and could not find any fault with it. The fact is we have tested it at home, on our own TV as well as on our home computer and it still freezes, same as when his mother operates it. We asked for a refund and the manager said that they could not do that as the manufacturer already received their money. We were told told buy another USB power-up part of R500 in order to use the hard drive properly, which is completely ridiculous.<br> <br> This was a gift and now it cannot be used for the purpose it was bought for. It is still within the warranty period, we would like to refund it. Why should the customer suffer? Your after sales service sucks. You have our money, now you couldn't care less what happens. We have been loyal customers of your shop for years, please restore our faith in you and let us refund this.