Samsung wants you to buy stuff using Samsung Pay. It wants you to so hard that it is willing to give you a free wireless charging pad if you do. Just activate the service on a Galaxy S6, S6 Edge, S6 Edge+, or Note 5.
A similar offer was originally open only to owners of Samsung's two larger flagships back when Samsung Pay first launched, and it came with an expiration date of October 11th. This time the deal is limited to a wireless charging pad and open to twice as many models. You need to have activated between October 28th and November 8th, must be at 18 years old, and have to live in one of the 50 US states or Washington DC. If you've already received a free wireless charging pad through the similar Verizon deal, then you're no longer eligible. However, the small print doesn't mention Sprint's willingness to give you a $50 bill credit for buying a device and activating Samsung Pay.
Samsung is limiting the deal to 200,000 chargers. Also, things won't ship for at least 8-10 weeks. People who registered in the past are still waiting to receive their gifts.