The qq mailbox sent a message saying that the qq account was changed to a secure mobile phone in Beijing.

In other words, your account has been changed to a secret mobile phone in Beijing. If this behavior is not my own operation, it is likely that the account was stolen by the person who stole the number. He changed his secret mobile phone and kept the account completely in his hand.

Solution: Open QQ, and click Retrieve Password. Enter the stolen QQ number. Click to change other authentication methods. Click Submit Data to verify. Click Start Authentication, fill in the identity information, and then click Next. Continue to fill in the data for verification. After the verification is successful, you can retrieve the stolen QQ. You can also invite friends to help verify the retrieval.