Change Active Directory CN without recreating account

How do I change an Active Directory CN without recreating the account. I have users that have changed their last names. I changed the Last name field appropiately, but the CN remains with the original last name.
For example, I have a users name that has changed from "Jane Doe" to "Jane Deer". I need the original CN name of "Doe,Jane" to change to "Deer,Jane" without recreating the account.