T-Mobile CEO John Legere has Sprint in his sights, predicting recently that T-Mobile will soon pass Sprint in total subscriber numbers. Now Sprint is working to make sure that that doesn’t happen by announcing a new promotion specifically geared at T-Mobile customers.

Starting today, Sprint will guarantee a minimum instant trade-in value of $200 to T-Mobile customers that bring their smartphone into a Sprint store and port their number to the big yellow carrier. The offer will run through April 9.

Sprint says that T-Mobile customers can also combine its new trade-in offer with its $350 contract buy-out promo. That deal will give eligible T-Mo customers a $350 prepaid or reward card to cover the remaining cost of their T-Mobile device when they switch to Sprint.