From the page:
"From 3 December 2017 you will not be able to subscribe to new digital content, apps or services from other companies through Premium SMS or Telstra Carrier Billing. This is because we're phasing out Premium Service subscriptions."
So it seems Telstra are phasing out carrier billing for Google Play, etc for prepaid customers.
——— CLARIFICATION!!! ———
I need to fix this after talking to a few people.
"Does the change affect all content?
No. If you have existing subscription services, or you add new subscriptions before 3 December, they will still appear on your Telstra bill or if you are a pre-paid customer, they will continue to be debited from your pre-paid account."
IT WILL ALSO NOT AFFECT ONCE OFF PURCHASES; FOR EXAMPLE - IN-GAME OR APPS THAT COST MONEY.
It will only affect NEW subscriptions AFTER December 3rd! So if you're not signed up to Netflix or the like yet, and are thinking about it, DO IT BEFORE DECEMBER 3rd!!
Sorry for the misleading information.
In saying that, bummer, because I was attempting to offload some vouchers I had to people who wanted Google Play credit and were on old grandfather plans that could use them, i.e. Freedom Plus, Encore, etc.
If anyone is willing to give me a hand, PM me, but just for general knowledge, I linked the FAQ / Crowd Support link above. RIP :(