e-mail was fine everywhere for me. If you're a little bit neurotic (and who among us isn't?) you can call to confirm as well. Probably best to e-mail, wait a couple days (a lot of them will send you confirmations), then call the ones that haven't responded.
Edit: Gah! I just remembered. I did have to call somewhere... I want to say it might have been UIC, but I can't remember for sure. They were nice and helpful over the phone though, whoever it was.