One trick to defeat Caller-ID blocking is to forward your phone line to a friend who lives in another LATA. When your friend receives the anonymous phone call, have him use *69 Call Return to dial to offending party back. As he is now placing a long distance phone call, the telephone number of the anonymous caller will show up on your friend’s phone bill at the end of the month.
A variation of this trick is available in areas where the local phone company offers per-call billing (as opposed to unlimited flat rate local calling) and where the local phone company issues itemized bills on those local phone calls. In those areas, you can switch your phone line to itemized local calling, *69 Call Return the anonymous telephone call, and read the anonymous callers telephone number at the end of the month.
If you are particularly anxious, you can often request your toll records from your local telephone company without waiting for your final bill.
In the United Kingdom, these techniques can be used by dialing 141 instead of *69.