I've had problems with this since January 2018.
Contacted Optus number of times via live-chat to have it stopped.
This sevice was blocked by Optus some time in March and i still get charged every month for the service i never signed for.
In January 2018 charge was $39.96, February $49.95, March $39.96, April $39.96, May $9.99, June $49.95.
Upto date i've been charged $229.77 for the service i never requested or signed for.
Every time i contact Optus i get promised that the charges would be credited back between 24-48 hours, that never happened.
After reading through forums general feel is that Optus somehow supports this scam.
Premium services should be requsted by the user i.e. Optus should not be enabling these service by default.
Not only that these services are enabled by defauld but Optus sets the limit to $200 per month.
My apologies for a longer post...take care everyone.
Thanks for reading.
Optus only blocked the premium SMS scam in March. Generally they involve a "subscription" so those would have remained in place. @Dan_C is pretty on the ball with handling these charges so you should get some relief.
If it doesn't work out, The ACCC recently required Telstra to refund on request to any customers that have complained about unwanted charges but been charged anyway. SO keep an eye out as its likely Optus (as the biggest and longest Premium SMS provider, will be making similar announcement at some point.