Hi i iam trying to book an earlier flight back to south africa from nz and to get hold of them is a huge struggle

Hi i iam trying to book an earlier flight back to south africa from nz and to get hold of them is a huge struggle. Nobody answers the phones the whatsapp agents takes up to an hour before replying. I see so many flights on their site for the same price as what i paid but then they come with huge qutes to fly back earlier. So why is the flights on the site and not removed. And the biggest problem i have they will not go out of there way to check any other date that is in the same price range and trying to help me. And being in nz i have to ask my wife to contact them and strugle with lack of help