Can the mobile phone bought by China be used in Korea? Install a Korean card

Yes, Unicom's 3G service usually automatically opens free international roaming service. Last time I went to Korea, my mobile phone received many SMS reminders from Korea. Text messages and phone calls are ok. SMS is deducted from your package and you can make multiple calls. I remember short messages that cost more than 3 cents. Receiving short messages is free. However, just in case, ask the customer service in advance if there is any international roaming. Mobile telecom also has international roaming service. I don't know the details. It seems quite expensive. Telecom needs more than 500 yuan.