I may be looking at the OP with tunnel vision but my reading is ‘the problem’ was the lack of communication in a change in how the transactions to Ozlotto were categorised leading to unexpected charges that also accumulated interest, not that the change happened.
For the change to have happened either Bankwest or OzLotteries would have changed something. Be it a correction or response to changed regulations. Ozlotto and TheLott both have similar ‘warnings’ posted. Ozlotto’s is a year old, TheLott’s is not dated, but it suggests it was not recent.
Even if BankWest decided it was ‘doing it wrong’ and is going to ‘do it right’ it is reasonable to me a customer should expect, and it would have been better business if not expected, to advise their customers that had potentially affected transactions.
Reading one’s statement on a regular basis usually works a treat to pick up on important things 
