The Galaxy S7 was an expensive phone when it came out a few months ago, and it still is if you go through standard retail channels. However, you can pick up a GS7 for the downright reasonable price of $499.99 on eBay today if you act fast. This is the dual-SIM (Duos) variant of the phone, and it's unlocked for use on any compatible GSM/LTE network.
As an international model, the Galaxy S7 Duos has an octa-core Exynos SoC instead of a Snapdragon 820. That may actually be a more desirable hardware configuration as many have reported better battery life. This phone supports all the main LTE bands for T-Mobile and AT&T in the US, including band 12.
You have your choice of the gold or silver colors (black is gone), and shipping is free in the US. Tax is paid only in Florida. The seller will ship internationally as well.