I've had iiNet as my internet service provider for...

I've had iiNet as my internet service provider for many years. They have the right plans for a decent price. They're an Australian company and I support local. I will soon have my NBN plan with them as well. I believe that they look after their customers better than Optus and Telstra.
Edit, there is no benefit to pre-book NBN over the phone vs the website. Both are same deals.