Went through to the answering machine, just missed the call. When I phoned the number right back, I got the 'Your call could not be connected' recording???

The initial call to me displayed "private". Indian lady wanted to confirm my contact details so that a representative could call at our home and give us a quote on solar panels, because the Federal Gov was now offering incentives "up to $4,000".
When the questions got more personal and I said I did not want to go any further so I hung up.
Then the phone rang again from the lady's "supervisor". He told me he was calling from India. However, the calling number display was (07) 5495 1792.
After I hung up I tried to phone that number back, only to be told that it was a disconnected number!!!
How can a phone call from India show up on my phone's calling number display as a local Australian number???????????????

Some woman called and wanted to confirm my name and that I had solar panels on my roof. I asked her not to call again. I'm on the do not call register.