XP Phone dialer won't use calling card for long distance

I have a ThinkPad with XP. I set up the dialer to use a calling card to make long distance calls (in the Phone & Modems properties in Control Panel).
When I try to make a long distance phone call to a contact in my address book, the dialer only dials the contact's destination phone number and does not dial the calling card access number first. I know the modem is working as I can make local calls with no problem. Any ideas on what's going on?
Thanks in advance for any help.