I need to visit Greek with a South African refugee document. Can I travel without a visa?
Using the passport of the country which you fled from is very risky, and not a good idea at all.
That's because a refugee using the passport of the country from which the refugee has fled makes a statement that they now accept the authority of the country from which they've fled. This will be seen as abandoning their claim to refugee status.
If the country that issued the refugee travel document learns of this use, it will likely cancel the refugee's travel document and the refugee's asylee status.