Received phone call from this number. Returned the call the same day and Optus advised number disconnected ? Weird

I didn't answer it but tried to call it back on a land line only to be told that the number has been disconnected. Grubs displaying an invalid phone number when calling and don't leave a message. Don't bother answering as I'm sure is telemarketing of some sort

Asked a lot of questions wanting yes/no answers (and got stroppy when they didn't come in that format) - suspect a scam.

Displayed as 061422727629. When I recalled the message came from Optus saying that the number was incomplete or incorrect.
I would approach your MP and argue that "INVALID" phone numbers should not be allowed to be used by telemarketing companies to hide their identity.