Return the call, recorded message ‘number not connected, check the number and call again’
I have blocked -SCAM

Yet another of the Indian scammers trying to sabotage their own economy, by destroying India's reputation overseas. They've successfully cost themselves billions in outsourcing contracts since nobody trusts them any more, and rightly so.
They use a lot of (03) 9125 05... numbers, I've had them with 0505, 0515, 0525 etc, and 05-something else. When I last picked up 6 months ago it was still the fake web developer BS.
Since then I have been blocking all numbers not in my contacts list using an app called Calls Blacklist. It actually works, if you block them long enough they finally stopped, though unfortunately I switched it off and they got through once or twice, and have started trying again. But, if every time they call they are blocked, they will finally give up, eventually