Bad and Non - existent service

I have been trying to contact this company now for days - I bought a dress from their store in Edgars Mall of the South for R1899 and unfortunately i picked up the wrong size. When I went there to exchange the dress they were sold out and would not assist me with getting another size 16. I did not have a receipt anymore but the price tags and all other tags were still in tack on the dress. I have tried phoning and emailing them but all i get is a message back the ticket has been closed. I need to get this dress exchanged.