From the AC documentation:
The attendant console server reads and caches directory entries at startup; after an initial handshake determines if the directory entries changed since the previous log in, the attendant console downloads the directory user list. The attendant console searches the following files for the user list, as indicated in the following order:
Specified user list file on the attendant console
CorporateDirectory.txt file under the User List Directory on the server
Automatically generated user list file on the server
The user list file exists in comma separate value (CSV) format and contains the following information:
Last Name
First Name
Telephone Number
Department
You could create a User List file on the local AC machine for each company. This will work, but will be a real pain to keep up to date. Everytime you add/modify/delete a user you will need to ammend the User List file.
HTH
D