T-Mobile's new promotion offers three unlimited data lines for $100 to new and current customers

In its continuing efforts to attract more sign-ups, T-Mobile’s latest promotion offers an additional line for free for accounts with two or more lines. The offer works whether you want to add an extra phone line or a line for wearables or tablets.

The deal is available for current and new customers — the amount of data available to the free line will match up with whatever your current plan is for the other lines. If your plan does not have the same amount of data between devices, the free line will get whatever’s the lowest of the bunch. Just two weeks ago, the company updated its T-Mobile One plan to include unlimited data for $100 a month between two lines. CEO John Legere said the free line promotion also applies this new plan.

The offer is available for a limited time, but be aware that it may take up to two bill cycles for the credit to show up. Although T-Mobile says in “most cases,” credit will show up in the first bill, you may be required to front the charges then get credited back in the following month. The offer begins on March 1st, and the free line is yours to keep even after the promotional sign-up period is over, as long as two other lines remain active.