Not a call center dingdong but they're literally not allowed to hang up on any potential money- they have strict rules typically and all calls are recorded in places that permit the recording- or at least potentially monitored- the boss could be listening at any time- some call centers are better than others, some do allow hangups if the abuse is bad enough, or transfers, but it's a rare place that does that.
I agree that an outbound sales contact centre are unlikely to hang up unless customer is abusive or feel the person who picked up the phone isn't the customer and is attempting fraud. I'd expect the AGL employee to advise they're ending the call, though.
Either way, DR should raise the feedback to AGL directly here.
As @Travong pointed out, an AGL staff member simply hanging up under the circumstances you've described would be quite unusual (and rude!).
It's entirely possible the caller was a scammer posing as AGL, and they disconnected when you would not share your info. AGL are a popular target for this purpose as we have a large customer base.
If you do have a complaint about an AGL staff member though, of course we want to hear about it, and it will be taken seriously. A good place for this would be the Complaints page.