Which telecom companies support Xiaomi phones in South Korea?

Hello, I would like to know if there are any carriers in Korea that support Xiaomi phones. Recently, I visited KT, SKT, and U+ stores, and they told me that they do not sell Xiaomi phones and that they do not provide services even if I purchase one myself. However, I understand that there are some offline Xiaomi stores in Korea. Then, I am curious about how people who own Xiaomi phones are receiving services. I wonder if the staff at the stores I visited gave me incorrect information, or if there are other ways to use Xiaomi phones. I would appreciate any advice on how people using Xiaomi phones have chosen their carriers or if there are alternative methods.