According to the Wikipedia information, South Africa has 11 official languages in the country. Of which only one is in the Untied Nations as the official language.
Would that be fair for the other languages ?
United Nations does not insist on the representative to speak in the official languages. You can speak in your national languages, well, since, South Africa practises equality, just doubt it, only 11 tribes of people in South Africa, they listed so many official languages.
Therefore, not to mistreat any of the other language speakers, the representative of South Africa is best speak Esperanto in the United Nations.
Read the language policy of United Nations
Watch the PM of India, Mr MODI spoke in what language ?