How did Yunnan Yitong know that he was blacklisted?

If the phone doesn't work, it's hacked. If it is banned or blacklisted, you can choose the serial number to reply in the personal center-contact customer service, and then choose to transfer to labor as required, leave your phone number and ID number, and reserve information as required. Customer service will handle it as soon as possible after seeing it. In addition, go to the hospital to find a volunteer staff of Dianyitong to help you solve it.