In December, 2005, the Premier warned of the dangers of drink spiking after his son's drink was apparentally contaminated at a schoolies celebration in Lorne.
Dont expect every manager to just crumble at your threat of consumer affairs. Get used to the idea of them telling you to go right ahead. There is a lot of red tape before it gets to the point of a business being fined. Consumer Affairs would first try to solve the dispute before taking full legal action.
A simple threat does not always do that much and will probably piss the manager off even more. Simply talking to the business owner rationally would be the most effective first option as was discovered in this thread