While AT&T has been touting the nation's fastest mobile broadband network, a new survey by Consumer Reports concludes that's not enough for customers -- "AT&T is the worst carrier."

Of the 58,000 ConsumerReports.org readers surveyed, AT&T received the lowest customer satisfaction score and was the only carrier to drop significantly. Of the AT&T respondents, more than half were iPhone users. According to the survey, they were "much less satisfied with their carrier and rated data service (Web and e-mail lower than owners of smartphones on other carriers."

These findings mirror those of an earlier study by Deloitte, which found that nearly half of all current iPhone users would be interested in switching to a Verizon iteration of the device, mostly due to overwhelming dissatisfaction with AT&T.

“Our survey suggests that an iPhone from Verizon Wireless, which is rumored, could indeed be good news for iPhone fans,” said Paul Reynolds, Electronics Editor for Consumer Reports.

Some other interesting findings of the CR survey: 

- U.S. Cellular, in a major coup, overcame Verizon Wireless as the top-rated wireless provider for contract service.

- Sprint, in "a remarkable turnaround," scored higher than Verizon -- the de facto leader in overall satisfaction since 2003 -- in some aspects, and pulled even with Big Red overall.