Hi all!

I’m using TP-Link Archer VR1600v however it seems to flat-out refuse to use any DNS server aside from what is provided to it from my ISP (TPG, Australia).
I changed the setting in Advanced > Networking > LAN Settings, applied, and restarted the router but it just will not use any alternate DNS Server.

Is it a common thing for modems to do? To lock-down settings?
Is this a TP-Link issue? ISP issue?
How can I make the modem apply this simple settings change?
Or who do I need to begin getting mad at?