The Galaxy S9 is also unlocked and will work on all four US carriers. That includes AT&T, Sprint, T-Mobile and Verizon in the US.
Samsung's Galaxy S9 might be a bit on the old side now, since it is a little more than a year old now, but at under $500, it's a good time to grab one. The Galaxy S9 is still going to be able to hold its own against other smartphones on the market, even those that were just released. And if you don't care as much about the camera, then it's a good choice. Not to say the camera is bad, but there's only one camera, and not three on the Galaxy S9.
It has a 5.8-inch Quad HD+ OLED display, with the Snapdragon 845 chipset, 4GB of RAM and 64GB of storage inside. There's also a pretty beefy 3000mAh capacity battery inside that will get you through the day.