The launch of the new Galaxy S5 smartphone in S. Korea was scheduled for April 11 but SKT preempted this, prompting KT and LG Uplus to start selling S5s as well.
SKT took the risk because it was scheduled to enter a 15-day business suspension from April 5 so sticking to Samsung's plan would have meant big losses.
Samsung had provided SKT, KT and LG with a limited number of handsets for marketing and pre-sales activities.
Following the early release, Samsung decided to cancel its official launch events in Korea and other markets.
The Galaxy S5 has a 5.1-inch full high-definition OLED display using active-matrix technology. It also features a heart rate sensor fitted under the rear-facing camera, which has also been upgraded from 13 megapixels to 16 megapixels.