They said that they were from Telstra, and that someone is using my internet connection for hacking and illegal activities. I asked them what kind of internet connect I have, and they deflected my asking me to confirm how many devices I have connected to my home internet. I responded by saying "Are you talking about my NBN connection?" (knowing that I am actually not in an NBN area, just to see what they say). They responded with "I am talking about your internet". I said "You are from Telstra... you must know what kind of internet connection I have" at which point they hung up.