AT&T is one of the largest communications holding companies in the world. The company also manages one of the largest Wi-Fi networks in the United States with more than 24,000 AT&T Wi-Fi hot spots, including locations in all 50 states in the United States. Based in Mesa, Ariz., it provides Internet-based communications services for businesses with virtual private network (VPN), voice over Internet protocol (VoIP) and other offerings. AT&T has spectrum licenses in the District of Columbia, Puerto Rico and the U.S. Virgin Islands. It is also a Better Business Bureau (BBB) accredited business.