Sprint is the only major network carrier in U.S. that still offers unlimited data plans. In order to lure in more customers, Sprint is on an advertising spree to promote its iPhone 4S unlimited data plans. Sprint is also offering $100 discount at minimum when you trade in another carrier's iPhone for Sprint's iPhone 4S.

The unlimited data plans come in different flavors. In Everything Data Plan 450 costing $80 a month, user gets 450 minutes of free voice service with unlimited data and text messaging. The Simply Everything plan is $100 per month offering unlimited voice service on Sprint network with unlimited data and text messaging. Also, you have to tack on additional $10 per month, which is a subscription fee if you are using a smartphone.

For more data plans for iPhone users, you can check the official page here.

Additionally, Sprint has also revealed that it will offer unlimited data plans for Apple's next-generation iPhone, dubbed iPhone 5, which is likely to pack 4G LTE radios. Sprint's hasn't launched the 4G LTE network yet, though the carrier has started launching LTE enabled android smartphones in the market.

On the other hand, both Verizon and AT&T are planning to roll out shared-data pricing plans this year. The shared data plans let consumer split Internet data on their phones and tablet giving an economical feature for family and small business usage. However, both Verizon Wireless and AT&T are hesitating to become the first company to test the success of shared plans in the market.

Verizon is nixing unlimited data plans. Even the company does not bother replying to consumer's inquiries regarding the death of unlimited data plans from the carriers. Customers are frustrated over the change in company's policies. Even long-term Verizon customers are planning to move away to other cellular network carriers like Virgin Mobile and T-Mobile. Meanwhile, Sprint Nextel is playing its ace to attract iPhone customers towards itself, which will eventually turn out to be profitable for the carrier.