Here’s a nice way to move out of March like a lamb (or a lion, depending on how clutch you think this play is): T-Mobile has been quietly referring customers switching away from a competitor to a promo site for 20 percent off their T-Mobile ONE plan rate “for life”.

A single line on the standard T-Mobile ONE plan will only pay $54 a month for unlimited data with full HD streaming and other amenities. And the discount’s good for up to 12 lines on any T-Mobile ONE plans, the only ones available from the Un-carrier after it scrapped its Simple Choice plans in January. Customers must attain a code from a service representative to input into the site for the discount to take effect. The promotion will be available through March 31.

Sprint recently promoted its competing Unlimited Freedom plan by charging $90 for between two and five lines on a new account.