I bought a Samsung Galaxy note in Korea and changed it to a sim card in China. Why can't I display my phone number? Can't reply directly?

Because the phone can't identify the local network frequency band. You can brush the machine. It is not difficult to brush the machine. Download a brush wizard, one-click brush, very simple, take your time. As long as there is no hardware problem with the phone, don't be afraid to brush it out. If it gets stuck in the process of brushing, buckle the battery back decisively. You can ask again if you don't understand anything. I can also brush Android. Other systems can't help you, but Android can.