WAN IP address is different from static IP given

[vbabiy]

I'm currently setting up OPNsense on my network and facing a configuration issue related to the handling of WAN IP obtained via DHCP and DNS settings.

My situation is this:

The WAN interface on OPNsense receives a dynamic IP address via DHCP from my ISP, Windstream.

Windstream also routes a specific static IP to the dynamically assigned WAN IP for my network's external access.
I want to ensure that the system or services within OPNsense use a predefined static IP for DNS and possibly other purposes, regardless of the dynamic WAN IP received via DHCP.

When I ever try to nslookup the router hostname I get the WAN DHCP IP and the LAN IP, but I am not able to talk to the router through the WAN DHCP IP.

Thanks for your help.