Question : DNS Problem on Adtran Netvanta 2100

I have a 10 year old Netvanta 2100 (1st Generation) that still works great, but we can't meet PCI compliance because the unit does respond to DNS querries, which upsets the PCI Compliance people.
The Firewall is configured with static IP from ISP, and I am using the ISPs DNS server names.
I have tried to set an incoming rule to block incoming UDP port 53 traffic, but that doesn't help.

I need to continue to use DHCP on the firewall so I can't statically assign the local machine adapters.

Answer : DNS Problem on Adtran Netvanta 2100

Can you post your access-lists and policies?