Said his name is Jack from the NBN and he informed me that my NBN account had been hacked and is being used or could be used by others. I asked him to provide some ID to prove who he was and that he was from the NBN. There was no usual pre-start to say that the conversation was being recorded, as Telstra and NBN usually do. When I asked him for his NBN ID, he said I didn't know what I was talking about. I then said I was recording this conversation and he hung up. Pretty dodgy behaviour for a genuine NBN employee.