What would you do if you opened up your cell phone bill to face a dizzying five-digit charge? You might do well to follow Mythbuster Adam Savage's lead. When the host of the Discovery Channel's "Mythbusters" learned he had rung up $11,000 in charges from AT&T while in Canada, he headed straight for Twitter. The culprit, he tweeted, was the USB modem plugged into his laptop that was running on a wireless plan suitable for the U.S., but not for Canada. "AT&T is attempting to charge me 11k for a few hours of web surfing in Canada. Pls RT!," he...