Hello @DarcyR. Have you had a look at your invoice to see what you've been charged for? Bills can be viewed online via your Optus My Account. If you’re having trouble locating your bills, further instructions can be found here. If you need further assistance investigating this, please feel free to send us a private message confirming your phone/ account number, full name, and date of birth.
It would seem likely you have been hit by the Premium SMS scam. Have you got any SMS lately about joining a subscription?
If you find so then:
1. Send STOP to any such SMS
2. Ask Optus to set your Monthly Premium SMS limit to $0
3. Ask Optus to refute the charges for you (they a required to)
4. Optus should get no answer to their refute and recredit the amounts to you next bill.
5. Tell Optus to stop enabling (and profiting) off this SMS scam