Hi Yols,
Thank you for reaching out, I'm sorry you have had trouble getting your plans changed.
I would recommend getting in touch so that one of our agents can change this for you, 24/7.
Alternatively, you can log into the AGL MyAccount at agl.com.au, or use the AGL app, available from the Apple App Store and Google Play Store, to change this yourself.
Kind regards,
Xander