Correctional Services spokesman Manelisi Wolela has denied allegations that student leader Mcebo Dla.
Mango, the low-cost airline recently launched by state-owned South African Airways (SAA), claims it "remains the lowest fare carrier despite competitor discounting".
But when shopping around for airfares, Sowetan found kulula.com to be the cheapest.
"I believe our fares are very competitive. We have no travel classes - business or economy class - as with most airlines but we have different fare classes," kulula.com marketing director Glenda Zvenyika said.
"Our pricing structure is a simple one: the cheapest fares per flight are bought first, followed by the next cheapest and that is how it works. This is inclusive of the airport tax," she said.
Airlines are notorious for advertising cheap flights, which then turn out to be far more expensive because the adverts don't include the Airports Company of South Africa's (Acsa's) fees.
According to Mango chief executive Nico Bezuidenhout, other airlines are now guilty of excluding Acsa fees in their advertised prices.
"The fact that some of Mango's competitors are now quoting both their regular fares and sale prices exclusive of taxes, means that consumers will pay up to 25percent more than the advertised pricing of some our competitors," he said.
Airfare quotes are likely to become more misleading in October when Acsa hikes its fees by 40percent to help cover its R20billion expansion programme for major airports ahead of the 2010 World Cup.
Acsa spokesman Solomon Makgale said the passenger service charges for domestic flights will increase from R12,27 to R38,59 while international flights will rise from R70,18 to R105,26. Makgale said passenger service charges are built into the airfares that passengers pay to airlines.