Is it possible to change my visa status in Newzealand?

Hi there, iam south African citizen holder iam planning to visit to Newzealnd , i dont need visa for my passport , its a port of entry, problem is they will give only short stay , when iam there, i want to change my status to student visa or permanent visa , i dont have much qualification is it possible for me please tell me what exactly i have to do. please give me all the details for long stay , i want to settle in newzealand, please help me out with all the details.