Well Switched the provider and they had it up and running within just 3 hours. Wasted 6 days without internet and chasing non-stop with AGL overseas customer care who have no idea what they're talking about!!
Just a quick update. My internet is up and running now. But the speed is not as fast as pre outage. I assume they are still working on the issue. I used to get close to 90 Mbps and now only 50mbps.
I received a SMS that there will be an urgent maintenance work tonight from 11pm to 1am. During that time, there won't be any internet. Hopefully this will fix the issue.