hangs up without saying anything

Caller: Opal HealthCare

I received a missed call from this number and when I called back I was connected to a woman from Opal Health Care. She was calling me about an online enquiry I made for aged care for my parents. I don't know why the number appeared as spam but it was a lovely conversation and they were very helpful.

Caller: An unlisted number, (02) 8528 4476

This was one of those scam calls who rings, and then hangs up without saying anything, intending you to ring them back.
There was no result found for the number 02 8528 4476, so I rang it to find out who the fraudster is. An automatic message came on, saying that my call was important, and to stay on the line and my call would be transferred to the next available agent. There was nice classical music in the background.

Eventually, a woman named Jessica came on the line. She knew my name without me saying it, and said they had tried to ring me earlier. She is from a company called SunMax, selling solar panels. I told her that I already have solar panels and a battery, and that the number she rang from is not listed in the phone book. I said that I only rang back to find out which disreputable company had tried to ring me, and then hung up.