If the number turns out to be listed on my bill, I hope I can recognise it and sort it out with the person myself.

If its just listed on the bill as private number, then I will take the information to the police, as they can get the phone number and details of this person from the phone provider (I can't because of privacy etc). I guess they'll either send them a warning or something, or even (in some cases like I have now read about) they may give me the last 6 digits of the mobile number.

But yes, hopefully they will get bored of it eventually...