"government" scam caller about electricity bill

Called my mum and she has tried to call back 10 times, no answer.
Judging by the other comments i assume it is no one important and probably linked to some marketing call center

Caller: No idea

Typical nuisance call, ring and hang up when you answer

Caller: NOT YOUR MUM

YOU NEED TO CALL YOU MUM MORE OFTEN,SOUNDS LIKE SHE SHE WANTS TO TALK TO SOMEONE

I found out about these calls that hang up / keep calling back /pretend to be someone
Particularly the ones who hang up either straight away or when you say hello
They are called Robo calls !
They can use your voice
So don’t say anything , even cough
If they say they are a bank or Telstra or something HANG up and ring your bank directly !

Caller: DID NOT SAY NAME

ABOUT A LETTER ONE WAS SUPPOSED TO HAVE RECEIVED ABOUT MY ENGERGY REDUCTION

On answering phone, silence, then hangs up.

Phone no. I didnt know when answered it was quiet i said this call being recorded for fed gov scam line , a computer said good by and disconnected

Keeps calling, rings and hangs up