Caller: Unsure

Had a call from 0488 848 731, then the same day I had a call from this number 0488 848 730 but no voice mail left. Tried calling back the first number but couldn’t hear any noise. Second number left no voicemail

Have received calls from almost identical numbers which I’ve tracked as spam calls.
Tried to call this one back and only had an optus disconnection message. I’ve blocked this one like the others.

Asked if he could talk to a "John Smith". Wanted to confirm if the "system was working" and hung up the call.