How to enter a contact's ext. # without auto-dialing it?

Is there a way to enter the extension for a contact's phone number when the company's phone system doesn't accept automated extension dialing? I used the proper procedure for adding an extension, but the switchboard operator picked up the phone as the extension was being dialed (after a pause), and she said I can't pre-program the extension. She said I have to call the main number and tell the operator the extension I want and then she'll connect me. I tried other methods of entering the extension without the pause technique, but I can't get "contacts" to accept it. Any tips? I just want to be able to list the person's extension next to their phone number for easy reference. Thanks in advance.