AT&T on Tuesday said it will run a trade-in promotion starting May 1 that will offer customers up to 50 percent off current smartphones. That means you could walk into a retail store with your old device—up to three years old in good, working condition—and get at least $100 off the Samsung Galaxy S4 or HTC One. That’s pretty enticing when you consider how very wonderful both of those handsets are.

The carrier is opening up the promotion to its current lineup of devices, meaning you can also get a discount on the iPhone 5, or even get the HTC First, which is $99, for free. AT&T said in some instances devices might have a value higher than $100, in which case customers will receive that determined credit. The more standard $100 credit is immediately redeemable in-store after trading in your old device. Put that iPhone 4 to good use and get your up-front device cost halved.

The promotion is running for a limited time—AT&T didn’t say when the offer will end—so you better take advantage quick if you’re eyeing up a new handset. In addition to enticing customers to try out new devices, AT&T said the promotion is a way to help consumers more easily recycle their old tech.