Two obvious possibilities, one being a rogue meter. Has it been checked to see what it does with power out? One way to check is if you have a monitor like a Powerpal (not a recommendation but a device the Victoria state distributes for free) so you can watch it in real time using your mobile phone. Got one, they are very informative. There are other similar monitoring devices.
The other less likely possibility is your grid operator has a corrupted database system and you are paying someone else’s bills. My experience was with Amex decades ago, posted here just to demonstrate how it can go. I’ll add this would be less probable today than it was then, and even then it was improbable yet happened.
If your Powerpal device shows use and the power is out you have hard evidence. If the Powerpal shows no use but your account shows use, you once again have hard evidence.
That approach is almost certainly cheaper and less stress than getting a sparky involved, although that might be necessary depending on how your subsequent interactions go with AGL.
