Unlimited data plans are a thing of the past. AT&T and Verizon still have a few users here and there on grandfathered plans, but they use every trick in the book to get them onto one of their tiered plans. It makes perfect business sense since the gatekeepers are allowed to charge whatever they want for paltry amounts of data. T-Mobile is looking to buck that trend.

Completely going against current industry trends, T-Mobile announced today that they will begin offering unlimited 4G data to their customers. The company says the new plan is perfect for “both data-hungry customers who want to experience all their smartphones are capable of and those wanting the peace of mind of never having to keep track of their data usage.”

“We’re big believers in customer-driven innovation, and our Unlimited Nationwide 4G Data plan is the answer to customers who are frustrated by the cost, complexity and congested networks of our competitors,” said Kevin McLaughlin, vice president, marketing, T-Mobile USA. “Consumers want the freedom of unlimited 4G data. Our bold move to be the only wireless carrier to offer an Unlimited Nationwide 4G Data plan reinforces our value leadership and capitalizes on the strength of our nationwide 4G network.”

T-Mobile is opening the new unlimited plan to both new and existing customers. New customers need only buy a new phone and they’re set with the new plan. Existing customers will only need to upgrade to the unlimited 4G plan when it becomes available on September 5.

Unlimited data is nice and all, but how much is it going to cost? Surprisingly, not much at all. T-Mobile says that a single line with the value voice and text plan combined with unlimited data will cost $69.99 a month. A classic voice and text plan with unlimited data will go for a bit more at $89.99 a month. It will obviously cost more for Family plans as the unlimited data will cost $20 per line on the value plan and $30 per line on the classic plan.

I can see customers angry over Verizon’s and AT&T’s new data plans moving to T-Mobile, but only if the carrier gets better phones. For one, T-Mobile doesn’t carry the iPhone and their Android line-up is severely lacking. The only great Android phone they carry is the Samsung Galaxy S III whereas other popular Android products are exclusive to Verizon and AT&T.

Regardless, it will be interesting to see how this announcement shakes up the mobile world. Will customers leave carriers like Verizon and AT&T for free unlimited data or will they put up with their current carriers for better phones? It’s a balancing act that consumers unfortunately have to play as carriers continue to evolve their plans for maximum profit.