T-Mobile recently rolled out a new deal that offers you a free line of service.
With T-Mobile's new promotion, eligible customers can get a third line of service for free after monthly bill credits. To get this deal you'll have to be a new T-Mobile customer or an existing subscriber with a single voice line.
New customers must sign up for two lines of service while existing subscribers will need to add a second line. This deal also requires you be on a Magenta or Magenta Plus plan.
If you meet those requirements, you can get a third line on your plan that'll be covered by monthly credits. Canceling any of your lines will cause the credits to stop.
Finally, T-Mobile says that there's a limit of 1 offer per account.
There's no official end date for this promotion, so there's no telling exactly how long it'll be available. T-Mobile only says that it'll be offered for a "limited time", so if you're interested in getting a free third line of service, you may want to act soon!