Another scam caller; number does not connect.

Called the number back and the phone display said “unallocated number” with a long single tone sound.
Scammers !

Getting a lot of anonymous call like this and they never answer the phone. How can we take action against these people? Please suggest.

I just had call from this number saying they are checking you have maximum discount of 25% on electricity account and you dont have to change suppliers - sounds dodgy....was hard to understand and I didnt give any details

But as soon as I answered and then hung up. I received a text about a bitcoin that had reached lots of money.
I don’t own bitcoin!

I called back number (03) 8202 3792 rang 3 times then goes to busy tone.

Nothing on the other end of the line

I never pick up, no message left. When I called back it said Optus regrets this number is disconnected.