I called back the number (02) 8318 0309 and reached vm that said the number is not in service

Caller: (02) 8318 0309

Calling non stop after midnight.

As I have received numerous spam and scam calls from various numbers, I didn't answer calls from this number. They called twice, after hours. I'm also on the 'Do Not Call Register'. The number is not registered on this forum. Therefore I decided to ring them (from a different phone). I got a recorded message, supposedly doing a political survey. Even if this is legitimate, I ask the question, why are they persistently ringing late at night? It is more likely just another scam and an attempt to get information. I would suggest extreme caution and preferably do not answer.