I rang back the number (02) 9136 1661, spoke with someone who hung up right away

One of many random landline calls I started receiving again recently. My email and phone number must have appeared in another dark web listing, so the scam calls have started to come in a new wave from new numbers after slowing down a little recently.
TIP - if they're calling your mobile, all you have to do is block any callers not in your contacts list and they cannot get through and eventually give up. On Android you can go to the blacklist and use wildcards, eg. (02) 9136 * so anything starting with those digits will be rejected. Also works for international numbers WRT one-ring or "Wangiri" scams, use eg. +2*, +3* etc so entire blocks of those strange countries you would never normally receive a call from can now get through. If you have relatives in a specific country add that country's code to your whitelist so they can call. Suddenly you will have peace! The phone never even rings when the scammers call, at last!

I phone back and the automated voice stated - "the number you have dialed is not in use". So clearly this is a spam call.

Caller: Supposed to be Telstra

Introduced himself and said he was from Telstra, and could hear a lot of people talking in the background, like a call center but when suggested that a lot of these Calle were scams, he pretended to get offended and hung up!
Rang back and message said "this number is not in use" so, probably scammers🤔

Caller: They said the NBN

Told me my phone and internet would be cut off… I hung up straight after

Caller: SCAM

Recorded message saying that my internet is going to be cut - total scam.