Caller said she was from Finder (https://www.finder.com.au/). Basically trying to switch over my gas/electricity accounts to a provider where they can get a better deal.
No doubt they're commission driven but may not have your best interests in mind for the long run, might just try to beat your current rate but not consider peak/off-peak etc etc.
But for you to know that, you've got to assess your own plan details - but really, it's not fun being put on the spot to then have to do the comparison when they want to call you.

The frequency of calls I get from them are often enough to be borderline harassment.

Caller: On behalf of Actewagl

Couldn’t catch woman's name, said she was from Actewagl, I said I had gone with another provider, she asked who and promptly hung up on me. Extremely rude. Actewagl says it’s probably a third party, not one of their team.

regular calls from this number, have not answered.