Parcel can not be found at the post office

On the 18 of Dec I went to Witspos in Ormonde,the reception lady said to my parcel has been sent to Randburg square.I just came from Randburg square post office they can't find it and rudely told me I need to check with Witspos in Ormonde because they haven't received anything on the 18 of Dec..I need this for my son school ...please