Update: Alrighty, thanks for your help guys. Much appreciated! I checked out your suggestions, and found Dodo to be the best/cheapest provider for our area.
So, long story short, we were originally on the TPG ADSL2+-Offnet plan, which included 300gb data (150 peak/150 off peak) for $69.99. My Dad (silly Dad) thought we could go on a better plan for the same price, so he tried to upgrade to an ADSL2+ plan, and we got a call saying that we can't go on that plan because our area doesn't have ADSL2+ coverage, and they can't put us back on our old plan because they've phased out that plan. Now, our options are 300gb for $80, or 500gb for $100 with TPG. Pay more for the same thing?!?! No thanks!!
So I'm on a mission to find a new ISP which will provide something similar to what we were already on. I'm pretty noob, the only really other 'cheap' ISP I know of is iPrimus, which is more expensive than TPG.
I don't want to give out too much info about where I live, but basically you probably won't be able to find any ISP able to provide ADSL/ADSL2+ to our area, hence why we're limited to offnet broadband.
TLDR; got kicked off our old internet plan, please help me find a new one with at least 300gb/month ~$70. Preferably with download speeds (torrent) of 1.3-1.5mbps (which is what I currently get on good days).
For that price point you're probably looking at someone like Exetel/aaNet/Eftel.
As much as people bag out TPG I have found their speeds to be much better than those above, so you may want to take that into consideration before signing any contracts with a new ISP.