sorry. I was thinking about something else when I posted my comment. Here is my instructions from my meet me user guide.
There is one extension setup as the controller of this meet-me bridge. That extension can change the access code. To change the access code, go off hook and dial XXXX followed by the conference call number and #, followed by the current access code and #. You should hear dial tone at this point. Now enter the new 6 digit access code and #. You will hear dial tone. Enter the access code again and # and you should hear 3 confirmation beeps. You can hang up at this point. The code has now been changed. You can change this code as little or as much as you need. All callers to the bridge will need the current access code to gain access.