Poor customer service from nedbank

Hi, I lost my money from my nedbank account, last year May. I then reported my issue with nedbank and they said that they're going to investigate my query and get back to me, but I haven't had any positive feedback from them til now. I always go inside the branch and query my issue with them but still no response from them still. This is pathetic, for such a institution. Could someone please help or advise me what should I do.