eBay has the Apple iPhone 6s 16GB 64GB GSM 4.7" Smartphone (Space Gray, Silver, Gold or Rose Gold) refurbished for $280 with free shipping. Features 4.7-inch (diagonal) LED-backlit widescreen multi-touch display with IPS technology, new 8-megapixel iSight camera with 1.5µ pixels, A8 chip with 64-bit architecture. M8 motion coprocessor, 1080p HD video recording (30 fps or 60 fps).
Has good Amazon Reviews.
Walmart has the Apple iPhone 6 32GB Phone for Straight Talk (Space Gray) for $199 with free shipping. List price: $399. Features 4.7" Retina HD display, Wi-Fi Capable, 8 MP camera/ 2 MP front facing camera, GPS capabilities, Bluetooth 4.1 wireless technology, Apple iOS.
eBay has the Samsung Galaxy S8+ Unlocked 64GB 6.2" Smartphone (Midnight Black) for $650 with free shipping. Retail price: $810. Features Snapdragon 835 Octa-Core (4x 2.35GHz + 4x 1.9GHz), 4GB RAM, 64GB storage, 6.2" Infinity display (2960 x 1440), 12MP cam, 802.11ac, Android 7.0 Nougat.
Walmart has the Straight Talk Prepaid Apple iPhone 5S 16GB CDMA Smartphone (Silver or Space Gray) refurbished for $50 with free shipping. Retail price: $129. Features 4G LTE, Corning Gorilla Glass, 8MP camera w/ 1080p video, A7 CPU, AirPlay, 4" 640x1136 Retina IPS LCD, nano-SIM.
eBay has the Refurb Unlocked Galaxy S6 32GB CDMA Phone (Black Sapphire) for $135 with free shipping. List price: $400. Features a 5.1" 2560x1440 QHD AMOLED touchscreen display, Exynos 7420 octa-core processor (Cortex-A53 1.5GHz quad-core and Cortex-A57 2.1GHz quad-core), 3GB RAM, 32GB internal storage, 16-megapixel rear camera, fingerprint sensor, and Android 5.0 OS (Lollipop).