Got a call, they said they're from AGL. I kinda believe them, but they started asking to confirm my personal details, so I asked for the reason of the call and said I'd call AGl back on the phone number on their website.

If you are not with AGL, then it'll be marketing spam.

Same as everyone else.
I was smart enough to block the number, they started calling from a private number

My 9yo son's mobile has had calls from AGL a couple of times this year. I called them back in May when he showed me he had had calls while he was in school and told them that he was a 9yo and had not had the misfortune of having to worry about an electricity bill as yet....and to remove his number from their database. They assured me they had done this. He turned on his mobile tonight and low and behold, missed call on the 31/7. The number is 9206 8900. I"ve been on hold for 10 minutes (though the repetitive message has been told me 5 minutes wait since I dialled in). I'm furious with them. My child is on a child protection order and very nervous about every little thing. When they call, he freaks out. I'll be asking for assurance by someone higher than the call centre worker who will answer the call, that he will never get another call from them ever again. If they do, I'll be reporting them to the ombudsman.

They have called me several times and hang up as soon as I answer.

Just got a call from this mob right now. Said my name and the call stopped.

I just had exactly the same experience. Scammers. Beware