If he was using calling cards and presumably pay phones he was paying dearly to be a pest. Sounds strange.
But most places have "Call Trace" (*57) in which the special unit of the telephone company gets a record of the call and has means of dealing with them. They charge about $1.50 per use, but if there is a repeat problem it's worth using. They can see more info than callerID, including blocked calls. I understand the special unit only gets involved if there is a repeat problem, not isolated incidents.
IMHO, the major carriers should bar calls from entering their system with faked caller IDs, such as VOIP systems that offer "111-111-1111".[TELECOM Digest Editor's Note: $1.50 per use? How about eight to ten dollars per use, which is more like it, at least in the case of SBC. I suggested to the chairman of SBC (or to the flunky who takes his phone calls and responds in his name) that telco should outlaw that all ones combination or all zeros, etc and when 'dipping in their database' to fetch the name, etc of the caller totally change all those entries to the essence of 'information denied by caller' (in other words, a *67 type call) and treat it accordingly. If I block *67 type calls -- which I do -- then I do not want all ones or all zeros either. Chairman's office told me that was quite impossible to do, and that if they delivered all zeros or all ones they had 'done their job and delivered caller ID' to me, so shut up and pay your bill. PAT]