Scammer addressed me by name and claimed to be from Telstra; trying to tell people their internet network had changed from private to public, and to get those people to provide remote access to their personal devices.

Got very defensive when I mentioned I wasn't a Telstra customer - then gave a long (and mostly untrue) spiel about how Telstra is responsible for providing all of Australia's internet
Mentioned that the network I was on had changed from private to public (it hadn't)
I made some rummaging / typing noises at my desk and said I was checking my modem to see if anything looked weird, scammer waited a few seconds then just said "oh my god" in an impatient tone
Made polite conversation to bide time for a couple of minutes
Apologised for not finding anything useful and went to ask for more details (to try to bait out more of the scam) and they hung up on me

Wasted some of their time, at least!