If you have recently received a malicious call and want to trace it, you can use a network code. This is most effective for harassment cases rather than simple spam.
You can’t directly “unblock” a specific No Caller ID number because it’s hidden by design. Instead, you temporarily disable all incoming private number blocks, then the call will come through normally. how to unblock a no caller id
However, if the caller left a voicemail, or if you use a service like (Last Call Return), you might be able to return the call. If you have recently received a malicious call