Welcome to AGL Community!
Although meter tampering is possibly, we find it to be very unlikely, there are a few things that can affect keeping in mind it is also winter so being home during this time and just the increase of winter could be factors. You can get more information of the energy usage in winter to help you see what the issue may be.
If you still believe someone else is using your meters power, simply turn your meter off, if only your unit loses power then you are fine, if you neighbours power goes off also then there may be issues there.
If you need further assistance do not hesitate to message our team through the AGL App or My Account.