It was only last year that many of the major U.S. mobile phone service providers eventually settled on a rate of $99.99 per month for unlimited, nationwide voice calls. This has been a boon for heavy users of mobile phones as it has brought down the cost of their monthly phone bills. But folks who also use their phones for data access usually have to pay an additional fee for that service. A few smaller service providers, such as MetroPCS and Cricket, are able to undercut the big companies by offering nationwide,