Landline dead for more than two weeks

[#1]

G'day

My case number is 20664841 and our business home phone is dead sicen 15 February.
I've hab about a dozen calls to the Optus herlp line, did four live chats, visited a store and now received four text messages telleing me, that the problem is fixed.
It certainly is not. The phone LED on the modem is still off and there is no dialtone on the phone. Internet is working well.

What eles can I do to make Optus' technicians work on our landline?
Emails to Optus bouce back marked "unread".

[#2]

Hi,
It's a little unclear from the fault reference number if it has been fixed, there is/was an issue with one particular landline number.
If you still need a hand, if you have a social media account, please send a PM to Optus on Facebook or a DM on Twitter with the details. 

[#3]

Hi Ray_YC,
thank you very much for your reply!
Meanwhile (after about 20 days) Optus was in touch with me. They claim

 "-It seems there is currently  outage for certain location which is still on going . "

I don't think that helps me at all. It simply looks like either Optus is unable to repair their own network or that Optus is unable to put sufficient pressure on the NBN-people.
When I was working in the heart of Africa we sometimes hat telephone outages for two or maybe even three days. Wild weather was often the reason. But here in Australia??? For 20 days?
I never expected something like this. Neither from Optus nor from the other one.

Regards
Dieter