Actually calling your telephone provider and getting the number for these people and reporting to the police may be a good idea, as they can get the Regulatory body for the industry aware of the situation and may be able to get something sorted
Wouldn't that be difficult though? Is there a worldwide ofcom or telecom register list?
I would personally say - "if" I got a phone call - oh I have just got your IP address and I am going to hack into you and wipe your data via my secure Linux server.... I wonder if that would be a nice, polite way of saying an expletive?