just change it after you add it...only takes a second, but there is no way to edit all of your contacts at the same time...unless you want to delete them all
If you don't have email addresses with the contacts, you can export them to Excel, move them, import them back into Outlook, and sync them back to your phone. I did this a month or so ago, and had to rebuild 1 000 email addresses that excel corrupted. Won't do that again. But the phone numbers are fixed.
also, when you add contacts from a call, it automatically selects work, so youll have to change it before you save the new contact. its pretty stupid how it does that i think