Hi Bluey,
Thanks for getting in touch!
If you're concerned about your tenant using power in your name, then the simplest way to resolve is to close your account. However, to your point, this may result in an interruption to their power supply! I recommend that you log into your AGL My Account (aglener.gy/MyAccount) and touch base with our customer service team via instant messenger to clarify the status of your account.
Kind regards,
Jayden