Rosebank post office useless service

It was last year that i sent my things using post office in rosebank. It was long before this corona and lockdown up to now when im tracking my things they don't show where they are. I went to post office in rosebank many times for them to assist me and when i get there they tell me that they know nothing. What makes me even more angry they tell me that them they did their part to send my things so i have to wait. When i ask till when should i wait they tell me that they don't know. I don't know what to do now im thinking of involving my lawyer because I'm not receiving any help from them. My tracking number is CN***ZA