I called back number 0409 865 920 rang once then gets disconnected automatically.

Same issues. This is a scammer!!!
If any decent person wants to talk to you they will a message with there contact details...(A..H...)

Received call. Did not leave a message. I called back and number is not even operational. Number didn't even ring. It is like the number is disconnected.

Never leaves a message.

Probably Credit Corp.

Caller: 0409 865 920

I answered the call and said "Hello" and waited. There was a hum but nothing else for several seconds, and then a - possibly recorded or synthesized - voice said what could have been my first name, and then the call disconnected.