Depends on a few things.
1) How are the calendars synced from the Server side? If your company is lumping all calendars into one 'account' (sharing everything at once), unless you have an option ON YOUR SERVER SIDE (either through Outlook's web app or your IT department), you will see all calendars in your phone because, to your phone, every appointment is tied to a single account.
2) The app you're using (if any). If you added the account through the phone's Account settings, AND the calendars are not being shared as a single group/account, then you should be able to go into the Calendar app, tap the menu button, and select the MANAGE CALENDARS option. There you should be able to turn on/off all calendars that are shared to your account (again, as long as they are shared as separate calendars and not through a single account/group). Just select the ones you want to see and unselect the rest.