What popular chat software is there in Korea, such as qq and Ka Kao? Can you speak Korean?

My Korean friends usually use pictures of Ka Kao and Line as evidence. There are many other chat softwares, but the penetration rate is not high, and not many people use them (after all, the population of South Korea is not comparable to that of China). Ka Kao can make voice calls. When I ask my Korean friends to correct my pronunciation mistakes, I use it.