YES - it’s a “yes” scam. The caller asks a question to which the answer is hopefully “yes”. They then put your answer of “yes” into a financial contract.
The question I was asked: “Do you have solar panels on your roof - yes or no?”

optus advises the number is disconnected

I rang back - just to check. “The number you have dialled has been disconnected.”
Female, heavy Indian accent. Asked if we had solar panels on the roof. I hung up. She rang back and said she wasn’t trying to sell me anything over the phone - and then proceeded to try to sell me solar panels.... Blocked.

Missed the call, but when I called back I got "Optus advises that this number has been disconnected". So I assume its a spam caller (same day we had a call on our landline about owing Amazon Prime $100 or some nonsense).