Hi Lamby04,
This is a very fair question!
In order for anyone to open an account with energy retailer, they simply require an address or meter number. If the the energy retailer, for whatever reason, attempts to open this account by mistakenly using the incorrect address or meter number, then it can unfortunately lead to situations such as yours. These incidents are more common in apartment complexes and subdivisions as opposed to stand-alone houses.
With hundreds (if not thousands) of Australians moving property every day, it is simply not possible for energy retailers check in with each individual prior to closing their account and instead attempts to transfer addresses between retailers are done so under the assumption that they've been lodged correctly. If they're not, we have means to reverse these transfers such as we have in your case.
Kind regards,
Jayden