Johannesburg International Mail Centre - My parcel has arrived but how can I get hold of it!!!!

I made an overseas purchase and the tracking number shows that my parcel arrived in South Africa and has cleared customs. I has been sitting at Johannesburg International Mail Centre since 23 January 2018, 6 weeks ago! I have tried contacting them telephonically since then on ********** , there is simply no answer! Not one of my 100's of calls have been answered. I've also tried sending emails. Also no response whatsoever. This is simply unacceptable. How can I get hold of my parcel?!