Non listed number.... software to fake voice... this number does not exist in any listing. Hang up

Recieved a call from company called Go Switch. Unsolicited sales call to save on energy Bullsh*t.

Calls and then hangs up. Waste of time. Do not bother answering just block this number.

I called back number (03) 4219 1302 rang once then goes to busy tone.

I called back number (03) 4219 1302 rang once then goes to busy tone directly.

every week this number keeps ringing mearound same time around 11 am, it's ridiculous. Im not wasting my time calling them back, if it was important then they should've left a message by now...

They phone and hang up without leaving a message. When I call this number back it is engaged.
I don't believe this is originating in Australia 03 Victorian numbers don't begin with 4, I believe it may be routed back to Australia from overseas.