PostNet Lack of any willingness to assist and/or communicate - missing parcel

On the 16th January 2018 my stepson send me a parcel from the Doornkloof PostNet branch (PPA ********** 33775). It was supposed to arrive on the 18th January 2018. When it did not arrived by the 19th January we went to PostNet Stellenbosch (Eikestad) to where it was supposed to have been sent. They assured us that it is on its way and will arrive the Fridayevening and we could fetch it from the Stellenbosch depot by the Saturday. At the depot on Saturday (20th January) they had the piece of paper that accompany the parcel but no parcel. They promised to follow it up. The next day I went back and still no luck. Unfortunately I had to leave for the UK the Sunday night. To date that was the last time anyone from PostNet has contacted me. Once back in South Africa I went back to the deport where the manager affirmed to me that no packet has arrived. While I was there (Monday the 5th February) the manager send an email to various people to follow it up, and promised me some response before the end of the week. Of course nothing materialized. The response from the Eikestad Postnet Branch is that it has nothing to do with them since the parcel has not arrived. The Postnet branch in Dorrnkloof has also not been very responsive. My stepson has been there twice now without any success or feedback. The manager is of the opinion that we should have taken the insurence option, which he himself lacked to mention to us. Furthermore he said in reaction to the possibility that we will mention this on social media that he advises against it since his "boss" has taken someone who has done that to court. In conclusion, the response and help from Postnet in this matter has been totally lacking, displaying no willingness to either look for the parcel or to communicate with me (us), just promoises and that is all, except for some not so subtle hints that we should not persue this matter by social media.