You could try this.
https://www.agl.com.au/residential/help-and-support/contact-us/do-not-contact-form

I answer call, they just hang up. It was AGL trying to sell me gas. I called back and they apologised and took me off their list. Easy

Mised call left no message. NFI who they are.

SCAM / dishonest / fraud = block number or report to Federal Police

They rang me last night and didnt leave a message. After reading the comments above I will be blocking the number.

I have been receiving many calls from various numbers but never ever a message left. I am so over all these random calls that dont leave a voicemail. I now never answer the phone unless I know who it is. My blocked callers list is getting longer every day.

Like most on this site, I receive multiple calls a day from this number but no message is left. I am bewildered to learn it is AGL. I am an ALG customer on a payment plan and I am actually in advance and have been for a while. Why would they call me?

Keep ringing leaving no message! I have blocked this nuisance caller

Agl no bill due just painful calls at all sorts of times how rude and unprofessional. I will be changing providers

Calls all time of the day and evening. I've checked my account is paid - there should be no reason for them to contact me - will be blocking the number from now on. Thanks everyone!

I answered once and got the start of a recorded message and a command to
"Press 1'. I pressed disconnect instead, and have received calls on a regular basis since.

Tempts me to move to a different provider.

Called me 6:25pm on a Wed in Sep 2014.
I answered it
After a few seconds they hung up without saying a word
:S

Calls my mobile multiple times a day so I blocked the number, now they have started calling my work which is a hospital.... Very poor form AGL

AGL - called about my gas connection....but there is no gas at my building.

Same here, 5 missed calls no message. If it is AGL I'm gonna change providers, sick of this c%$p

Got an inconvenient call from them at 18:40

Once I found out how AGL were ripping me off compared to my neighbours, I switched suppliers. Now they constantly hassle me trying to win me back. Too little too late.

Calling everyday for the last week and never leaves a message.

Calling 2-3 times a day, every day! Even at 8pm at night

Keep calling me and won't leave a voicemail message.

AGL telemarketing. Telling you what a great plan you're on and how wonderful AGL are. (maybe I should have asked her for a date?)