KEVENZ&reg; Km-300S 3G Senior Cell Phone, Simple and Easy to Use, SOS Button, Big Buttons, Unlocked Elderly GSM Phones for At&t and T-mobile (KM300S) Designed by KEVENZ in USA, Assembled in China, this phone is compatible with either the AT&T or T-Mobile network. Service can be purchased without any contracts from either provider. Easy to see phones , Phones with Big buttons makes it easy to dial with one hand. display gives large, easily readable characters. The dual SIM slots take the larger SIM cards from AT&T and T-Mobile not the tiny ones. Easy to dial phones, Cell Phone Clear loud voice that says the numbers as you are dialing. numbers keypad size is 1.3*1cm,and display font size is 1.0cm*0.8cm&#xFF0C; especially for anyone with a poor eye sight to use. Easy to hear phones, large cell phone with a large speaker on the back, They can hear the speaker phone at a noisy bus stop. There also has a place to attach a lanyard(strap). The SOS button on the back is a great feature that can be programmed to dial 911 or 3 additional phone numbers. Kevenz for making you feel that your Aging Parents and grandmother is safe and secure with this unique piece of technology! Unlocked cell phones are compatible with GSM carriers like AT&T and T-Mobile as well as with GSM SIM cards (e.g. H20, Straight Talk, and select prepaid carriers). Unlocked cell phones will not work with CDMA Carriers like Sprint, Verizon, Boost or Virgin.