Pathetic unfriendly service

My son gifted me a pair of hi-tec's he bought at Total Sport but was too big. Tried to exchange it at Total sports Westgate Mall Mitchell's plain since Monday. First their systems didn't work to do the exchange when I got there Monday. Showed them the gift slip to do the exchange and they said they will keep the Takkies I must check in again the next day, which was yesterday. System still not working. Called today they advised the system is working to do the exchange. When I got there I gave the lady the gift slip but she credited my son's account with the value of the takkies and tells me she can't exchange the shoes and there's nothing she can do. My question... What is the use of the gift slip then if we can't do an exchange??? I was and still am highly aggravated as the service was pathetic and now leaves me without my hiking shoes. Can someone get back to me to resolve this issue please. Unfriendly and not even an apology just plainly tells me in a hostile manner, we can't give you the shoes and There's nothing we can do !!! No we apologise, or we will find out HOW we can assist you. I am not leaving it at this I am taking this further. This is unacceptable.