Caller was a female with Indian accent. Called saying she was from Telstra and that somebody was accessing my internet without my usage (note: I don't have Telstra as my NBN ISP). When I asked to clarify if this was for NBN, she said yes. Asked me to get to my computer to start changing things. I tried to call her bluff by asking for a phone number I could contact them back on to work through the issue at another time and she hung up.