The Lumia 640 carries a 5-inch LCD screen with a 720 x 1280 HD resolution. That works out to a pixel density of 294ppi. The Snapdragon 400 SoC is under the hood featuring a quad-core 1.2GHz CPU, and the Adreno 306 GPU. 1GB of RAM is inside along with 8GB of native storage. Those seeking additional memory can access the 128GB capacity microSD slot.
An 8MP camera adorns the back of the unit, and a .9MP snapper on the front of the phone handles selfies and video chats. A 2500mAh battery keeps the lights on, and Windows Phone 8.1 is pre-installed.
AT&T's GoPhone pre-paid service has three tiers of service. All three plans come with unlimited talk and text, and unlimited messaging to Mexico, Canada and over 100 countries. The $30 a month plan allows you to purchase 100MB of data for $5. The $45 a month service ($40 with auto-refill) comes with 2GB of data and rollover minutes. The $60 a month plan ($55 with auto refill) comes with 5GB of data, rollover minutes, free talk and text from the U.S. to Canada and Mexico, and free talk and text in Canada and Mexico.
source: Walmart, BestBuy via WMPoweruser