Compatibility summary
You will need a travel adapter in South Africa; plug types used there differ from Australia.
Plug comparison
Australia plug types: I
South Africa plug types: C D M N
There is no common plug type between Australia (I) and South Africa (C D M N). You need a travel adapter.
Voltage comparison
Australia: 230V, 50Hz
South Africa: 230V, 50Hz
Voltage difference is within a range many devices tolerate; check your appliance label.