Brett, your situation is not unique. I have been having the same problem since Saturday with my Yahoo Small Business-hosted e-mail. The support phone numbers have been out of service since Dec 2, according to an online post, and you will find that you are on hold for 10 minutes or so, then you get a busy signal and it's time to try again. I tried a Yahoo billing number, which was closed for the day at 3:00 PM Central time.
Customers are being asked to leave a message through the online Contact Us page. When you do so, you will get an automated response with a case number, and then you will probably get a message a day or so later saying the case has been closed, even though the problem has not been resolved. Send another message, and other than the automated e-mail response, you probably will get nothing.
Yahoo, this is no way to treat business clients who are depending on you to support their businesses.
Source: Personal experience after hours of trying to contact Yahoo Small Business