The new mobile phone rate schemes are encouraging subscribers to change telecom companies and forcing carriers to expand marketing to retain customers.
According to the companies, SK Telecom added 466 new subscribers on Friday whereas KT lost 59. LG Uplus lost 407 subscribers.
The shift took place after the three mobile carriers launched cheaper data-oriented payment plans.
SK Telecom recorded net growth of 313 mobile subscribers on Thursday, a day after the company launched its data-oriented payment plans. For SK Telecom, this was the first time in 122 days it had recorded a net increase in subscriber numbers for two consecutive days.
The company also said more than 150,000 subscribers, including existing SK Telecom users, had signed up for the new plans on Wednesday.
According to data from mobile market researcher DooIt Survey, 63.8 percent of mobile subscribers who were considering using one of the data-oriented plans chose SK Telecom. Those who answered that they will use KT and LG Uplus were 25.4 percent and 10.8 percent, respectively.
The survey revealed that 32.4 percent of the respondents who chose SK Telecom said they were attracted by its unlimited free voice calls to wired and wireless lines.
Unlike those of the other two carriers, SK Telecom subscribers can choose a 29,900 won plan that includes unlimited free voice calls to wired and wireless lines. KT and LG Uplus offer unlimited free voice calls only between mobile phones for payment plans at that rate.
In the same survey, 47.6 percent of respondents said they did not make calls using wired home phones because they could use a mobile phone's unlimited voice calls instead.
SK Telecom announced its data-oriented plans a week after LG Uplus rolled out similar bill plans. KT was the first to introduce the new plans on May 8.
KT attracted more than 100,000 subscribers for the new plans in four days after their release. LG Uplus recorded more than 100,000 subscribers in a week.
Expectations are that KT and LG Uplus are likely to conduct aggressive marketing to contain SK Telecom after the launch of the plans.
Some online handset retailers allegedly offered illegal subsidies to lure subscribers. The retailers said they would offer "21 bags of coffee beans," which means 210,000 won in cash payback, for those who changed their mobile carriers to use a data-oriented plan.
"Some such online retailers have caused customer damage in the past by luring them with fake promises of illegal subsidies," a telecom industry source said.