The FCC is looking into Truphone's ties to Russian billionaires, including Roman Abramovich, the owner of Chelsea FC.
Three Russians are major shareholders in a steel company.
Truphone, which owns a small US carrier called iSmart Mobile, had misrepresented its ownership structure, meaning foreign entities were able to take control of the FCC-approved licenses.
A series of complex ownership structure changes for Truphone were outlined in a notice from the FCC.
The agency said thatTruphone failed to accurately report its ownership structure and failed to get Commission approval before an unvetted foreign individual/entity acquired more than five percent of the company.
The FCC launched an internal assessment of Russian ownership of telecommunications interests in the United States in the wake of Russia's invasion of Ukraine.
The UK and the European Union have imposed sanctions on Roman Abramovich, but not on the US. Neither of them are sanctioned.
FCC commissioner Geoffrey Starks said that the individuals have been targeted with sanctions overseas.
He said the action was about keeping the US networks secure.
The United States and other democracies around the world were rethinking their policies towards entities affiliated or subject to the jurisdiction of the adversary states after the invasion of Ukraine.
Truphone has 30 days to pay the fine or file an appeal.
Truphone said in an April 1 statement that it is not subject to any sanctions.
Truphone did not respond to Insider's request for comment immediately.