check your commsec order confirmation, page-8

Conspiracy theory time.

It was a HFT bot run by an institutional criminal organisation which saw your order at .004, somehow ripped a matching order off the .003 buy queue, then pushed it to the front of the .004 sell queue to sell it to you at a handsome 33% profit all made in less than a second.

All this while the hapless ASIC not only turns a blind eye, but actually endorses this kind of reprehensible behaviour.

Seriously though, not sure what happened to you, but I think if you placed the order at .004 max there's not much scope for you to complain if that's the price you paid. Unfortunate, yes, but that's the rub.