Mailing to Australia.

I mailed a parcel to Australia on 11 April 2019 from Kollonade Pretoria. It cost me R322.70 and a tracking number RJ 031 814 915 ZA. ON 20TH May I enquired. The parcel was received in Johannesburg on 16 April. Today the 20th May the parcel is still in Johannesburg. What can I do to get my oarcel back from the worst mailing organisatin in the world?