I presume your 'service' is with the big T.
It might be worth asking if Optus have a local wireless service, They probably won't have the speed of the big provider at its best, but probably don't have the customer load either. Amaysim and Internode wireless both use Optus as the provider. I have a couple of Amaysim powered devices. Not blindingly fast and nowhere near as quick as my hard wired ADSL 2, but acceptable for portable work. And then there's Vodaphone, but in my observation they generally shun the country.
Your can't be only one thus affected by this - complaining formally might help but I imagine the answer will be soothing, but essentially "that's how it is ...".
And like you, I imagine that the NBN promise will disappear into the black of debt well before we are favoured with its presence and availability.
fOr