Telstra have announced they are to kill off third party billing arrangements in December. It is your turn now Optus.
Unfortunately Optus have a history of long association with these services (a decade ago Optus owned half of all premium SMS services). Not sure where it stands now.
It is a despicable business practice and the revenue raised shouldn't be worth the customer anger and dissapointment it creates, let alone the morass of complaints that customer service have to waste their time answering. Optus is a $10 billion dollar company and should not be actively assisting scam operations to make a few million profit.
As @Davelew says, ball's in your court Optus.