Not only is T-Mobile offering unlimited data, there is no fine print telling you that once you go over a data cap your data speed will be throttled or you'll be charged overages. The carrier calls it the "ultimate worry-free experience". Starting a week from Wednesday, the Classic Unlimited Plan will be $89.99 a month. That means that you merely add $30 to the $59.99 Classic Unlimited Talk and Text. Value Plan customers need to add just $20 a month for unlimited data.
it does offer some pretty fast data speeds. LTE will be coming to the operator next year. In the meantime, heavy data users are going to be thinking long about making the switch. The timing of this decision for T-Mobile is perfect considering that Verizon and AT&T have already publicized their shared data plans and can't easily return to unlimited data. T-Mobile still doesn't offer the Apple iPhone though, but still has some potent devices to offer heavy data users, like the Samsung Galaxy S III. And according to the operator, the Classic Plan with unlimited everything will save you $240 a year over AT&T and Verizon's 4GB monthly data plan with unlimited talk and text, and Sprint's unlimited talk, text and data plan.
If you're planning on signing up with T-Mobile for unlimited data, better tie a string around your finger, because so many things are happening on September 5th that it wouldn't be unusual for you to forget about this. On that date, a joint Motorola/Verizon event is expected to result in the introduction of the eagerly awaited Motorola DROID RAZR HD. Also on that date, Nokia and Microsoft are scheduled to introduce the first two Windows Phone 8 powered versions of the Nokia Lumia line. And the next day, September 6th, Amazon is rumored to be introducing the sequel to the Amazon Kindle Fire.
source: T-Mobile via SlashGear