Easiest way would be from a system administrator mailbox. To access....
1. Call your mailbox.
2. Press SA (72) for the System Administrator Menu.
3. Press DS (67) to delete the security code.
4. Follow the voice prompts.
System administrator is usally an operator phone or some supervisor. A system admin mailbox will not ask you to press 72 for admin features, you just have to go ahead and do it. If you get in, great, if not try another extension.