Subscribers of MTN, which prides itself in offering coverage "everywhere you go", had no network over the weekend.
Company spokesman Brigitte Bhengu yesterday attributed the network crash to a "software lockout" which, she said, affected mostly subscribers in Johannesburg.
Bhengu was quick to allay fears of a repeat on New Year's Eve.
She insisted that the MTN network had been upgraded to handle the festive congestion of calls and SMSes.
"The software lockout is something we did not anticipate," Bhengu said. "We are not battling with the flooding of the network."
She said MTN users in the coastal areas, where many people have gone for their holidays, had not experienced the problem.
"It was mainly in the Johannesburg area but the problem has been sorted out."
She assured the 14 million MTN users that the network had been upgraded and that they would not experience problems on New Year's Eve.
"We know that phone calls and SMSes on New Year's Eve triple. We have a network to handle the volume," she said.
Meanwhile, users of "South Africa's leading cellular network", Vodacom, complained about the slow movement of SMSes and MMSes on Christmas Eve.
Vodacom spokesman Dot Field said her company had a state-of-the-art network management centre that monitored the network used by 24 million people.
"As is the trend, voice, SMS and MMS traffic greatly increases over the festive period," Field said. "Naturally, because of the increase, some delays might have been experienced."
Cell C spokesman Karin Fourie claimed their coverage had been exceptionally good.
"Our subscribers had no problem on Christmas Day and we are positive that on New Year's Eve we will not encounter problems," Fourie said.
She said the 5,4 million users of Cell C were an exception when it comes to technical problems experienced by other networks.