I am compelled to offer you one of the four gems of philosophy by which I try to live my strata life: Never attribute to malice anything that can just as easily be ascribed to stupidity.
Your strata manager has a pothole in their invoicing procedures and you have fallen foul of it. A polite letter asking for a refund and a new system that is less likely to trip you up, should be enough (if you aren’t already at daggers drawn).
If you are, what do you really want? Your money back? To make a point? Or an easy life. One and three are achievable. No 2, less so, but you could say that you will be writing to other owners recommending that they find a new strata manager at the first possible opportunity.
That said, remember the five favourite words in legal circles: “It’s a matter of principle.”