Earlier quoted context omitted.
If people are in the store I’m responsible for and they blackmail me I would call security or the police, too. That‘s unacceptable behavior. I understand your frustration, and it really sucks that Telstra put you into that situation, but that doesn’t make your behavior ok and excuse abuse of employees.
Who said anything about blackmail or abuse of employees? The GP said he asked to speak to a manager and, I quote, " wasn't being threatening at all ." I don't see an issue with refusing to leave a store when you're denied a refund you're legally owed. That's literally the least threatening form of protest one can make.
So you may as well just go to McDonalds and ask them for a refund.