Sprint Nextel may now become a heavy hitter in iPhone competition. The carrier confirmed Wednesday that its iPhone 4S will come with the option of an unlimited data plan.

The company reportedly bet heavily on the iPhone, committing to $20 billion for an order of 30 million iPhones over the next four years.

Sprint has three calling plans that will all include its unlimited data. A $69.99 plan will now come with unlimited data, text messages, 450 calling minutes and unlimited calling to any cellphone in the country. An $89.99 plan comes with 900 minutes on top of the data, text and mobile-to-mobile calls, while a $99.99 plan features unlimited access to all services.

Meanwhile, Verizon and AT&T started their tiered data plans in June. AT&T offers 200MB of data at $15 per month or 2GB at $25 per month. Verizon offers three different data plans: $30 for 2GB, $50 for 5GB or $80 for 10GB.

Sprint hopes an unlimited data plan will be enough to reverse its trend of contract subscriber losses and irestore its revenue for profit. Many customers have left Sprint to nab the iPhone from Verizon and AT&T. Now, its ad campaigns that mock the tiered plans can really take off with the addition of the iPhone 4S.

Nevertheless, with benefits come costs. According to CNET, while the iPhone would stabilize its customer base and bring in higher-revenue customers willing to sign long-term contracts, it would also lay a considerable financial blow to the company in the short run. Sprint is expected to pay a $500 subsidy per phone.

In order to stay in the game, Verizon and AT&T are already justifying their cases as the best iPhone carrier. On Tuesday, Verizon sent an e-mail to reporters touting its network quality, which it believes sets its iPhone apart from the others. AT&T, meanwhile, said that its iPhone 4S would be the only one to connect to the faster HSPA network, and also touted the availability of the free iPhone 3GS. Sprint will not support the 3GS because the phone only connects to the GSM network, which is not compatible with Sprint's CDMA/EVDO network.

Sprint being able to sell the iPhone will only drive further iPhone sales for Apple. Sprint will sell both the new iPhone 4S (a $199 16GB model, a $299 32GB model and an all-new 64GB $399 model) and the older iPhone 4 for $99.