US wireless providers have agreed, under self regulation, to ".. send free alerts to help consumers avoid unexpected overage charges". The FCC peruses bill shock prevention for long time now (here).
The move was announced jointly by "..CTIA President & CEO Steve Largent(pictured), Federal Communications Chairman Julius Genachowski, and Consumers Union’s Communications Policy Counsel Parul Desai"
"The plan – called the “Wireless Consumer Usage Notification Guidelines” – will provide free alerts both before and after subscribers they reach monthly limits on voice, data and text. In addition, the plan includes a notification to inform consumers of international roaming charges when traveling abroad. Subscribers will be covered by this plan unless they opt-out .. By October 17, 2012 participating carriers will provide customers with at least two out of the four notifications for data, voice, text and international roaming and all of the alerts by April 17, 2013".
See "CTIA-The Wireless Association®, Federal Communications Commission and Consumers Union Announce Free Alerts to Help Consumers Avoid Unexpected Overage Charges" - here.