KT lost 310,000 subscribers over two weeks after waiving cancellation fees in the aftermath of an unauthorized small-payment incident.

The telecoms industry said on Tuesday that 312,902 KT subscribers left between Dec. 31 and the previous day. Even after accounting for inflows to KT, the net loss was 179,760. Including departures to MVNOs, the decline was 238,062.

Over the same period, SKT and LG Uplus posted net gains of 162,953 and 47,772, respectively. Including MVNOs, the net increases were 165,370 and 55,317.

A large share of KT leavers chose SKT. Of the 312,902 subscribers who left KT, 201,562, or 64.4 percent, moved to SKT. Another 70,130, or 22.4 percent, switched to LG Uplus, and 41,210, or 13.2 percent, ported to MVNOs.

Total number portability on Jan. 13, the last day of the fee waiver, was 83,527. KT lost 46,120 subscribers, including 28,870 to SKT, 9,985 to LG Uplus and 7,265 to MVNOs.

A total of 664,476 people switched mobile carriers during the two-week period when KT implemented the cancellation fee waiver. The daily average was about 47,000 cases. An average of 22,000 people left KT each day during the period. In particular, 31 percent of all leavers were concentrated over two days, Jan. 12 to 13.

About 350,000 customers left from Sept. 1 to Dec. 30, when KT decided to refund fees retroactively. Adding that period, the number of customers KT must refund is estimated at about 660,000.

The industry views the fact that more than 60 percent of KT leavers chose SKT as largely due to a membership programme. SKT runs a programme that restores subscription tenure and membership tiers if customers who left during last year's breach incident rejoin.

An industry official said, "Considering that daily average number portability is about 15,000 cases on normal days without issues such as flagship handset launches or cancellation fee waivers, an unusually large number of moves occurred." The official added, "All three carriers implemented large-scale subsidy policies, stimulating demand among customers switching carriers."

Some retail channels also saw handset shortages. The Galaxy S25 and Galaxy Z Flip7 were notable examples.

KT will take refund applications from Tuesday through Jan. 31 on its website, via its customer centre and at KT stores nationwide. Eligible customers are those who cancelled KT service from Sept. 1 last year through the previous day.