Moody’s Investors Service predicted Monday that KakaoTalk operator’s launch of a free phone-call service will negatively affect the credit ratings of the nation’s two major telecommunication operators.

“The launch of VoiceTalk is credit negative for our rated Korean telecommunication operators, SK Telecom (SKT, A3 negative) and KT (A3 negative),” the global rating firm said in a statement.

Its view comes a week after Kakao, the Korean operator of popular multi-platform texting application KakaoTalk, unveiled its plan to launch a free phone service called “VoiceTalk.”

Moody’s forecast that VoiceTalk is likely to enjoy a similar level of take-up as the texting application, KakaoTalk.

“A switch to greater use of VoiceTalk will threaten telecom operators’ voice market, which amounts to a key, but declining share of their revenue.”

SK Telecom and KT will face “additional burden in capital expenditure from an increase in data traffic” and suffer from a “negative impact that the new service will have on operators’ average revenue per user in the voice segment,” according to its projection.

The rating firm, in particular, highlighted the situation that about 34 million users, accounting for over 65 percent of the nation’s mobile subscribers, are texting via KakaoTalk.

Pointing to the texting service’s rapid growth in Korea, Moody’s said, “We estimate that about 60 percent of smartphone subscribers from SK Telecom and 55-60 percent of such users from KT are, therefore, eligible to use VoiceTalk for free.”

It said a driver for smartphone users’ shift to more expensive plans is the maximum number of allowable minutes to make phone calls without incurring additional, incremental charges.

“Thus, the availability of VoiceTalk’s free phone service is likely to encourage customers to migrate to cheaper plans that yield less average revenue per user for the telecom operators,” it said.

Currently, telecom operators permit smartphone users paying at least 54,000 won ($46) in basic monthly fees to have unlimited 3G data service and to make voice calls using mobile voice-over-Internet protocol at no additional charge, Moody’s added.

By Kim Yon-se (kys@heraldcorp.com)