How to get your VOIP phone working when you churn NBN providers (using the old ISP's modem)

We recently moved from ADSL to NBN (I know, right?) with iiNet and in the process, they changed our Toolbox to one which TPG has been using since probably 1990 or something. There was no longer the daily bar charts of data usage and instead an interface that wouldn't even let you change your payment method. This was enough to cause us to shop around, landing with Exetel with their $60 NBN50 month by month offer.

It took about five weeks for them to finally get the VOIP transferred over from iiNet, while we were paying for both iiNet and Exetel. This was when after two hours of digging around in the modem settings, I came to realise that internet service providers are locking people out of the VOIP settings when they give you a modem. The router we had from iiNet which worked perfectly with Exetel's NBN wouldn't let me see the Telephony menu! The only way to overcome this is to find out your super-user login details for your modem. That is, instead of logging in with admin/admin (and then changing your default password), there is a login for example with TP-Link's vr1600v router called su (for super user). The default password for this login is a little tricky to find but once you find it, you can change your SIP settings from iiNet to Exetel as well as the login and password for that VOIP phone line to work.

For the TP-Link vr1600v, this is how you find out the su password.

1. Login to 192.168.1.1 or whatever it is for you (eg 10.1.1.1?) in Google chrome
2. Go to the Advanced menu then click on USB Sharing 
3. Right click on the web page and clicking Inspect
4. Click on the USB Storage Device
5. In the Inspector screen, click on Network at the top and you should see a list of CGI lines. One of them has cgi?5&1&1&5&5&1&5&5&5&5&1 - click on this 
6. You will see the contents pop up in the right hand column.  Now scroll down and you will see something like this 

1. adminName=su
   adminPwd=ygRW52!au8

7. Your super-user login is su and the password is ygRW52!au8
8. Logout of your modem and login using the above
9. You will now see the Telephony option and you can replace the SIP Details with that of your new NBN provider.