This story has been updated with comment from T-Mobile.

T-Mobile USA has been ordered by the U.S. Labor Department to pay more than $345,000 to a whistleblower.

The employee at T-Mobile's Bellevue, Wash. headquarters was fired in April 2009 after raising concerns that international business customers were being fraudulently charged for roaming, the government said.

The Labor Department said the fraudulent charges reached into the “millions” but did not further specify how much T-Mobile had allegedly overcharged its customers.

"This case clearly shows the department's commitment to ensuring that individuals are provided the protections and relief afforded by the law, and sends a strong message that retaliatory actions will not be tolerated," Dean Ikeda, Seattle's regional administrator of the Occupational Safety and Health Administration (OSHA), said in a statement.

OSHA's Seattle office led the investigation that resulted in the government's order against T-Mobile yesterday. Whistleblowers receive legal protection against retaliation from their employers under the Sarbanes-Oxley Act.

A T-Mobile spokesman said the company plans to appeal the order and will provide evidence that the employee was fired lawfully.

"T-Mobile acted appropriately in ending this individual’s employment which was unrelated to any concerns he raised," the spokesman said.

The charges T-Mobile has been ordered to pay include $244,479 in back wages and interest, $65,000 in damages and $36,493 in attorney's fees. T-Mobile has been ordered to reinstate the employee and train its other workers on whistleblower provisions in Sarbanes-Oxley.