This was inevitable. The old Windows eventvwr scam moved on (in Australia) to the scammers claiming to be from Telstra and then to claiming to be from the NBN.
It's funny how long some of them will argue with you if you tell them that you are not with Telstra.
What's not funny is that some of them are now threatening to cut off your internet if you don't do as they say. There are sure to be people who would believe that.
If you have the time, I'd suggest you string them along, right up to the stage when they want you to download and run remote control software. Try to get the code from them and then report them. (Some of the reputable remote control software sites have an option to report scam users. If they say they are from Windows, there's a Microsoft page to report them too.)
Then see how much they swear at you when you've wasted 45 mins. (I cooked and ate dinner while on one of their calls once.)