AT&T and Verizon have already switched to tiered data plans to keep costs down, but T-Mobile has been steadfast in keeping its "unlimited" data plans available for all smartphone owners. However, the tide may be changing, as it has been revealed that T-Mobile plans on reducing (or "throttling") download speeds when customers' data usage hits 5GB in a single billing cycle.

T-Mobile's data plans previously held a 10GB ceiling (nothing is really "unlimited"), but now with more and more apps using cellular signals to download movies, make calls, and stream music, data is in higher demand, which means a higher cost for wireless companies and customers alike.

Are you a T-Mobile customer who uses a boatload of data every month? Find out how T-Mobile will be alerting you of your overage, and how to check your current usage, after the break.

Once you hit your 5GB data cap, T-Mobile will send you a free text message alerting you that your data speeds will be slowed until your next billing cycle begins. To check your current usage, log into your T-Mobile account and click on the "Monitor Use" tab.