My old modem was an NB1300 so there's definitely a firewall there.

You don't have to buy a static IP address...it's not something you have to get from Westnet. You can just set one up yourself for your computer. These are the static IP instructions.
PortForward.com - Free Help Setting up Your Router or Firewall

Have a look through those & you'll see what you have to do. Print them out if you think it'll help (I did).