maybe the heat Foxy had the same trouble here twice last week it was the heat
use Optus wireless[NBN]

Firststep, talk to your Internet Service Provider (ISP).
Which you are doing.
Telstra may well ask you to do something like your Indian friend got
you to do so they can look at how your modem is setup.
When I had intermittent trouble like you they, Telstra, found it was
the setup in the local exchange.
Here's a thought, was your area blacked out last Friday ? Has it only
been intermittent since Friday ?
In my case there had been major work in the exchange and the Telstra
equipment was reset to default values. Because I am well over 2km from
the exchange my ADSL2 line needed "tuning" so to speak.
When they fix it, ask for some detail about what was wrong.
If it happens again, repeat that detail back to them and it might
save some time,
In my case it was the exchange modems paramaters that they changed.
They, the tech on the phone can do it remotely.

Have fun !

Well, now I'm well and truly back and everything
has been fixed - thanks to Telstra.

I finally ended up calling Telstra and telling
them that I could not access either the internet
or my emails. They sent out a field technician.
He was here for about two hours testing everything.
Finally he found that we had corroded connections
at the street junction leading to the house.
He replaced the main telephone point in the house
and ran a new line to the computer. It was part
of the Telstra maintenance service - and everything is
now working. I couldn't be happier.

Dear Bazz,

Thanks for your advice.

It got me good results.