Fair Credit Acts and Identification

Aren't these companies supposed to identify themselves when they call even if they leave messages on voicemail? Also aren't they supposed to have their ifnormation show up on caller ID? I finally was able to track the number that sometimes shows up; other times they show up as annonymous. Again isn't that also a violation of fair credit acts? They call me at least 3 times a day other weeks it's every hour on the hour for 13 hours. They always just say this is so and so (first names only) and it is imperative that you call my office today at 800XXXXXXXX. Their tone is so nasty. I don't know what makes them think that I'm going to call back if they are not going to bother to tell me who they are or what they want. This has been going on since May. I'd like to konw what I can do to get them to stop. They also keep reaging this on our credit report so it'll never come off. It was from July 2002 and at this rate, it'll never come off our credit report. Anyway, is there anything we can do to stop this insanity without making matters worse for us? Thanks for any helpful advice you can give us.
Marci and Jon