1. Confirm identity: either confirm identity for subsequent business processing or unsubscribe. The last four digits of the ID card are the last four digits of the ID card number, which can be used to verify your identity information. If you don't know your service password, China Telecom may confirm your identity in this way.
2. Survey information: You can also check the user information to understand the user's usage and feedback.
In any case, if you are suspicious or uncertain about these calls, I suggest you first check with China Telecom's customer service to avoid personal information being leaked or used by bad elements.