I called back number (03) 8234 3452 rang once then gets disconnected automatically.

I rang back and a message said the number was not connected

I never answer,
I wait to see what happens after the phone stops ringing,
then look up this site to see if anyone else has been called by the number, then block.

selling something

Cock sucker

Missed call, no message, number disconnected when rang back

scam artist

Caller: electricity company

about switching electricity provider and not friendly

Going on about electricity discounts. An absolute flogger of a person. Wouldn't listen to anything said in return. Not interested in changing providers. There should however be a law against this as the call crackled somewhat and was difficult to hear. There was also a lot of chatter in the background, as in like an offshore call centre. In the end, hung up on him.

Didn't leave message.

No message left.

I also called back number (03) 8234 3452, which rang once then gets disconnected automatically.

I called back and it says disconnected. Sounds dodgy

When you call the number back - recorded response says: "number not connected"...so it's a scam, don't answer.

scammers

I didn't pick up they didn't leave a message

Hung up as soon as I answered