Sprint customers can choose to lease a Galaxy S7 on the Galaxy Forever program for $25.99 per month for 2 years, and get another S7 for $0 per month after a $25.99 service credit. If you don't want to join the Galaxy Forever program, you can choose Sprint's Installment Billing: pay $27.09 per month for 2 years for a Galaxy S7, and receive a second handset for free after a $27.09 service credit. Mind you, the buy-one-get-one deal only includes the regular Galaxy S7, so you can't use it to get a free Galaxy S7 edge.
In addition to offering this Galaxy S7 BOGO deal, Sprint also has something for Apple fans: if you switch to Sprint, you can get an iPhone 6s 16 GB for $13.17 per month on the iPhone Forever lease plan - if you trade in your old smartphone. Normally, the iPhone 6s 16 GB costs $26.39 per month, so that's 50% off the monthly price.
You can find more details about Sprint's latest offers at the source link below (and in Sprint stores across the US).
source: Sprint via Twitter