Carrier Locked to AT&T Wireless. Cannot be used internationally or on any other cellular carrierPower-infused performance Loaded with all the power you need, the Lumia 640 LTE works as fast and efficiently as you do. It's a workhorse that lets you concentrate more on what you're doing at any moment, with its quad-core Qualcomm Snapdragon 400 processor and Microsoft Office built in. And you'll have plenty of juice to help you achieve more with the whopping 2500 mAh battery. 2G GSM 850 / 900 / 1800 / 1900. 3G WCDMA 850 / 1900 / 2100. 4G LTE band 850/2100/1900 (1700/2100) mhz..