Caller ID, which is short for caller identification, is a feature that many people have come to depend on. It allows the user to identify who is calling before answering the phone. You may not feel like speaking with certain individuals and caller ID gives you that option. If someone calls from a private number, you have no way of knowing who is on the other end of the phone line. There are ways to find out who is calling from a private number, but it may not be an instant unveiling of the mystery caller.
Dial *69 after the call has ended. This option is available on most phones. This will call the last incoming number to your phone. Listen for familiar voices on the phone, if someone answers, or on the answering machine.
Keep a log of the private calls if they are happening frequently. Write down the time of the call and if you recognise voices in the background. Keeping a log can lead you in the right direction if a pattern is being formed. You may be able to connect the pattern to someone that you know.
Contact the police if you feel that you are being harassed and not getting any closer to identifying the unknown caller. Bring your call log so that the police can use the log to identify the private caller. The police can also monitor your calls to trace the calls of the private caller.