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T-Mobile's competitors have learned from its tricks and are now using some of its tactics to woo customers back. Sprint on Friday announced a new initiative to attract customers away from T-Mobile, and it comes with a guaranteed payout for your current smartphone.

The carrier said that it will pay at least $200 for your current handset, in addition to $350 per line that you move over to Sprint's network. Sprint said the $200 is available as an immediate trade-in credit and that the $350 will be passed to customers as a prepaid or reward card that's good for covering the early-termination fees from T-Mobile.

As for customers on other carriers, Sprint will continue to match those offers.

Sprint said the T-Mobile deal lasts until April 9 only, and that customers can only trade in one device per line. The deal is final, too, so you won't be able to get your phone back.