Quick Guide to top cell phone carriers

National carriers offer service across the United States. They offer a broad range of services with standard monthly plans that require contracts. Most offer month-by-month prepaid plans as well. National carriers are mostly retreating from "unlimited plans," and are beginning to offer shared data plans for multiple devices, which typically benefits family groups most. Within these structures, you can buy a data allowance of several gigabytes (GB) per month.

National carriers

After acquiring Alltel in January 2009, Verizon Wireless became the biggest wireless carrier in the United States. It was one of the first carriers to offer a 3G network, a music store, and GPS services. Also, it was the first carrier to offer a mobile TV network. Verizon launched its 4G LTE network in December 2010, though its first 4G-ready phone, the HTC Thunderbolt, didn't burst forth until March 2011. A joint venture between Verizon Communications and Vodafone, Verizon Wireless was formed in 2000 through a merger between GTE Wireless and Bell Atlantic. In June 2012, Verizon nabbed another first, this time pioneering shared data plans.

Things you should know about Verizon Wireless:

• This carrier requires new subscribers to choose a shared data plan, which charges a device access fee and offers unlimited talk, text, and hot-spot connectivity along with your data tier.
• Verizon's 4G LTE rollout will cover 400 markets by the end of 2012
• Every new smartphone will be 4G LTE-compatible
• Of the major carriers, Verizon has received several awards from J.D. Power and Associates for the best network, and more recently for customer service
• Its smartphone selection is varied and includes the iPhone, Android smartphone, and BlackBerry. The carrier is expected to reintroduce Windows Phone with OS 8 in time for the 2012 holiday season. It acquired the <a href="http://reviews.cnet.com/8301-19512_7-20030471-233.html">Apple iPhone in February 2011</a>.
  
• Its Friends & Family option offers unlimited calling to a select group of numbers, even landlines.
• As a CDMA carrier, Verizon's international coverage is limited to a handful of countries but it offers dual-mode CDMA/GSM handsets.
• This carrier offers prepaid plans.

What do CNET users think of Verizon Wireless? Its fans praise its "killer service" and "perfect coverage," while its detractors complain of "poor customer service" and call it "locked down and overpriced."

AT&T is the second largest wireless carrier in the United States after Verizon Wireless, at least for now. In March 2011, AT&T launched a failed attempt to buy T-Mobile, which, if approved, would have pushed AT&T past Verizon. Today, AT&T offers a widespread network and a large and varied selection of cell phones and smartphones. Originally formed in 2001 as Cingular Wireless, it changed its name to AT&T in 2007 to reflect its parent company. In 2004, Cingular acquired the now defunct AT&T Wireless.

Click here to see to see AT&T's coverage map.

Things you should know about AT&T:

• In July 2012, AT&T followed Verizon in rolling out shared data plans.
• AT&T's grandfathered "rollover" plans let you roll unused minutes over to the following month.
• Carrier operates a GSM network, AT&T offers extensive international roaming.
• Its 4G LTE network trails Verizon's in terms of coverage, but it does offer fast 4G speeds.
• AT&T has picked up some of the trendiest phones soon after their release date. It was the first carrier to offer the Motorola Razr V3 and spent two years as the exclusive provider of the Apple iPhone.
• Has a varied selection of smartphones with all major operating systems and is a major Windows Phone supporter.
• This carrier offers prepaid plans.

What do CNET users think of AT&T? Its fans say it offers "great service with cool phones" and the "best coverage out of the top carriers," while its detractors complain of "bad product and worse customer service" and say it is "epically terrible."

Following a 2005 merger, Sprint Nextel is now the third largest wireless carrier and the second largest CDMA carrier in the United States. The company folded in Sprint and Nextel brands, and is phasing out its iDEN network. It will retain push-to-talk service through Direct Connect. Sprint began wireless service under its brand in 1995, and Nextel was founded in 1987. Prepaid service is available only through its Boost Mobile and Virgin Mobile subsidiaries.

Click here to see Sprint's coverage map.

Things you should know about Sprint Nextel:

• This carrier continues to offer unlimited calling and data plans.
• Sprint's WiMAX 4G gambit failed, and it is the third of the major carriers to launch its LTE network, behind Verizon and AT&T. As of July 15, 2012, Sprint's LTE operated in 15 U.S. cities.
• It was the first major U.S. carrier to introduce a 4G (WiMax) network and phone, the HTC Evo 4G in June 2010
• Its handset lineup includes a large selection of Android smartphones, the iPhone, and BlackBerry.
• Sprint has a robust eco-friendly line and offers several rugged phones.
• International CDMA has a smaller footprint than GSM, though the carrier now offers dual-mode CDMA/GSM handsets.

What do CNET users think of Sprint? Its admirers say it has the "best bang for your buck" and "flawless service." On the other hand, a critic complained of "hideous service and billing, with stores manned by zombies" and another said "what a joke!"

The second-largest GSM carrier in the United States, T-Mobile grew out of the former VoiceStream Wireless in 2001 when Germany's Deutsche Telekom acquired VoiceStream. T-Mobile operates one of the smaller U.S. networks of the big four carriers, but it has roaming agreements with AT&T and other smaller operators. In May 2011, it launched its fastest-ever HSPA+42 "4G" network, but a potential $39 billion buyout by its only national GSM competitor, AT&T, set T-Mobile back in maintaining its network and competing with other U.S. carriers.

Click here for T-Mobile's coverage map.

Things you should know about T-Mobile:

• This carrier offers unlimited calling and data plans.
• T-Mobile's Wi-Fi calling app lets you make phone calls when the network connection is weaker
• As a GSM carrier and a subsidiary of Germany's Deutsche Telekom, T-Mobile has extensive international roaming and thousands of Wi-Fi hot spots in the United States and Europe.
• Of the major carriers, T-Mobile has, in the past, received the highest customer service rating by J.D. Power and Associates
• T-Mobile is applying much of the $4 billion cash injection it received from AT&T's failed takeover to invest in improving its network
• It was the first carrier to launch a Google Android phone. Its smartphone lineup now includes Android, BlackBerry, and Windows Phone devices, but no iPhone.
• T-Mobile's plans are some of the most competitively priced among the major carriers. In 2009, it introduced Even More Plus plans that don't require a contract, but don't offer subsidies for phones. Its Even More plans require contracts, but come with hardware subsidies.
• This carrier offers prepaid plans. It's upgraded HSPA+ network offers 4G-like speeds, though it is not technically a 4G technology.

What do CNET users think of T-Mobile? Opinions range from "best service with least amount of problems" and "the least evil cell phone company" to "irresponsible, unethical company" to "too many dropped calls."