Quote from actual problem- "user states they have a problem with a DNS
file on a server and needs to modity it."  They then provide a user
ID.  And then they state "they need to change their ID" within the DNS
file.....What does this mean? and how is this accomplished?

A DNS (Domain Name System) file is what "points" systems to the
right place (server) where a web site, or mail server, etc. is
located.  It is almost unheard of for a "user" to modify a DNS
file; this is the realm of the System(s) Administrator, etc.

There isn't a "user ID" entry in a DNS file; inside a DNS file
are entries that can point a domain name (domainname.com, etc.)
to a server (by name (some.server.net, etc.) or IP number (such
as 1.1.1.1, etc.) and can also contain information about where
the mail server for that domain name is located (in the above
format), etc.

Depending on the operating system (Linux, Windows, etc.) the
method of changing the DNS information varies, but the DNS file
for a domain is edited (I used a plain text editor on the Linux
network I used to admin) then saved and (with some systems this
is automatic) the DNS services are restarted.

The above is a simplified (and as much as possible) nontechnical
explanation of what needs to be done.  Any changes to DNS entries
should be done by someone qualified to do such operations.

Hi
As per your question
1. "user states they have a problem with a DNS file on a 
server and needs to modity it."  They then provide a user ID.  

This sounds like the problem which zone file/entries. 
You need to check if their domain name resolves.


2. And then they state "they need to change their ID" within the DNS file

This could be change in either Domain name 
 or May be "ID" should be read as IP . 

DNS file will be the zone file

Please let me know which OS (UNIX/Linux/Windows/Other) Used

3. .....What does this mean? and how is this accomplished?
Need more information

Regards