How to remove duplicate phone numbers from Contacts?

For some reason I have one contact card that got messed up and now has a boatload of phone and fax numbers from all sort of other contacts. Is there a way to remove those duplicate phone numbers from this contact card if they are already on another contact card? I could go through it one by one, and search for each number, but it doesn't seem to be an efficient way, particularly when there might be other contact cards that have the same issue. I'd be willing to pay for a (not too expensive) app if that does the trick, or keen to try a command line or AppleScript solution as well.