T-Mobile starts offering free 30-day network trials in specific U.S. locations
If you want to begin your 30-day trial with T-Mobile, you'll have to pair a dedicated trial device with your smartphone and keep it with you to call, stream, and browse. Naturally, the trial doesn't cost anything, but there's a 30GB data cap which ends your 30-day trial when reached. Otherwise, you can continue to use T-Mobile's network for 30 days if you don't use all the data during that time.
The bad news is the 30-day trial is only available in specific markets across the United States: Boston, MA, Austin, TX, and Atlanta, GA. Also, keep in mind that current T-Mobile for Business, MetroPCS, and customers of T-Mobile partners using T-Mobile network are not eligible for the trial.
And finally, once you've participated in the network trial, you won't be able to get into it again for 6 months since the moment it ended. To enroll in the 30-day trial, simply sign up via T-Mobile's website and you should receive the free trial device via free 2-day shipping.