Fonus is an American telecommunications company based in Santa Monica, California, operating as a mobile virtual network operator on AT&T’s network. Founded in 2019 by Canadian businessman Simon Tian, the company offers a single monthly prepaid plan as opposed to the usual multi-plan offerings of other carriers, providing users with unlimited data, unlimited calls and texts worldwide, and free roaming in the United States, Canada and Mexico at a fixed monthly fee. The data operates on AT&T's cellular network in the United States, whereas the calls and texts are provided through Fonus' proprietary voice over IP (VoIP) application. As of April 2021, Fonus is one of the top 10 best-rated mobile network operators worldwide on TrustPilot.