The four data tiers are described in a T-Mobile brochure as "unlimited" although an added note points out: "If you use more high-speed data than your plan covers, we simply allow you to access the Web at up to 2G speeds."
Other U.S. carriers, including AT&T, which is seeking , tend to charge more when a data limit is exceeded while keeping the speed the same. In fact, T-Mobile had been adding an overage charge of 10 cents per megabyte for its 200MB data plan first introduced last November. The carrier eliminated the overage charge today on the 200 MB plan and instead implemented the speed reduction, a spokeswoman said.
A previous $30 unlimited data plan had been subject to a speed reduction at 5GB of wireless service, although that speed reduction was apparently not widely known.
In all, the four new T-Mobile plans for data are: $10 for 200MB; $20 for 2GB; $30 for 5GB and $60 for 10GB.
The spokeswoman said that when a limit is reached, T-Mobile will send customers a free text message advising them of the limit and giving them the option to change their plan to a more expensive one with more data, or continue using their current plan with reduced data speeds until the reset of the billing month.
T-Mobile has said its high-speed data network at 4G speeds with HSPA+ can reach 21Mbps on an uncrowded network, while its 2G network, also called EDGE, can drop down to below 100 Kbps.
Tiered pricing plans such as T-Mobile's are gaining steam, with AT&T the first to do so last year, charging more than T-Mobile at $15 a month for 200MB of data and $25 a month for 2GB.
Verizon Wireless said it plans to introduce data pricing tiers this summer on and is considering , similar to how voice minutes are pooled.
As part of T-Mobile's announcement, the company noted that an unlimited family plan for two lines will cost $139.99 per month, which includes voice and text and 2GB of high-speed data. Two weeks ago, the carrier had announced a similar individual plan for one line costing .
In addition to the four new pricing plans, which require a two-year contract, T-Mobile also announced two new pre-paid monthly payment plans that incorporate speed limits on 4G service. They are $50 for unlimited talk and text and 100 MB of data at 4G speeds, and $70 for unlimited talk and text and unlimited data with the first 5GB of usage at 4G speeds.
Matt Hamblen covers mobile and wireless, smartphones and other handhelds, and wireless networking for Computerworld. Follow Matt on Twitter at or subscribe to . His e-mail address is .
in Computerworld's Mobile and Wireless Topic Center.