Why does “Call Blocking & Identification” often turn off automatically?

The main reason for this situation is the instability of the iOS system. We had reported this problem to Apple. This problem often occurs after upgrading the Whoscall version. After upgrading Whoscall, you are suggested to enter Whoscall App and confirm whether the "Call Identification" function is normally activated. Furthermore, Whoscall will send you a notification if the function is closed.