I had an order in with Comsec (I use the commsec website interface) to sell some shares but no one met my ask price so the order just sat open. I can't remember exactly when it was (I think it was Monday evening), I logged into the commsec website and cancelled the sell order. It was well before the opening of the exchange on Tuesday 1st July. I clearly recall seeing the screen you get after cancelling an order that says that the cancellation will be placed with the exchange when it next opens.
I am quite gobsmacked to find a trade confirmation in my inbox and to see that the trade happened today (Wednesday 02/07). Interestingly the sell order got filled with two trades, both cross-trades. I've opened a ticket with Commsec. I'll have to keep a log and record all my orders, cancellations and amendments from now on.
Has anyone else ever had this problem?