Technically, it is illegal for South African firms to collude with one another to set prices
The government created this regulation to prevent the companies creating a high price that couldn't be afforded by the citizen.
For example, if all oil companies in a country colluded to set the price, they could both set up a high price for their products in order to obtain maximum profit.
If they're not colluding, on the other hand, they will compete to set up the lowest price possible in order to attract consumers.