Hey guys. Just letting you know to not answer these calls.
Any silent call that you answer identifies your number as being "active" (A number that is currently being used), and puts you on the market for any scams or telemarketing. Try not to answer any calls from unknown or private numbers, because if you do not pick up for certain periods of time, your number will be listed as inactive. That's a good thing, meaning they are less likely to call back.

I had 3 calls one after the other. Firstly +64 3 668 5409 (NZ), I hung up, immediately my phone rang with number (08) 7477 7921 (Adelaide), I hung up, immediately after hanging up my phone rang again with number (08) 7905 4742 (Darwin). I'm located in QLD, I suspect they were trying to spoof a landline number in my area but failed.
I didn't answer any of the calls but I suspect it was a scam.

Just got a spam call. Don't answer it. (08) 7477 7921

Missed call, no message.

You do undestand that by picking up and hanging up you are answering the call? You can't state you dind't answer, that's why they kept callin you back from other numbers.