Best thing when someone like this calls is tell them nothing, just say point blank you do not want the work done.
You have to be carefull, sometimes they question you to suss out whether there is someone at home, did you report the matter to the police Marpalian.......A man was sat outside my house one day in a car, but seemed to be acting suspiciously, I reported it to the police, and to their credit, they did act upon it, and it was an innocent person, but I didnt know it at the time.
People do say what is the point of reporting it, the police wont come, but they definateley wont if you dont ring and try to report the incident.