By Marina Lopes

WASHINGTON, July 3 (Reuters) - Accusations by a U.S. agency that T-Mobile US Inc charged customers millions of dollars in unauthorized charges were sensational and exaggerated, its chief executive officer said on Thursday.

On Tuesday, the Federal Trade Commision filed a complaint against T-Mobile, the fourth largest U.S. wireless carrier, accusing the company of charging customers for subscriptions to services for which they did not sign up.

"The FTC certainly did a good job of sensationalizing their story and their news at the expense of both T-Mobile's reputation and mine," said T-Mobile's outspoken CEO in a company blog post.

"T-Mobile has in the past and will continue to keep our pledge to bill customers only for what they want and what they have purchased for as long as I am CEO of this company!" he said.

The FTC declined to comment.

While T-Mobile carried services from third-party companies from 2009-2013, it ceased partnerships with the companies last November and instituted a refund program to help customers who were charged for services they did not authorize, he said.

During that time, T-Mobile billed customers for the subscriptions on behalf of the third-party companies, which were responsible for getting customer authorization, Legere said.

In its complaint, the FTC said the subscriptions were for services like horoscopes or celebrity gossip, delivered by text message, which often cost $9.99 a month. T-Mobile received 35 percent to 40 percent of the amount charged.

The Federal Communications Commission said on Tuesday it was also investigating the matter.

In the post, Legere dismissed the complaint as "Washington politics" and "big carrier lobbyists at their best." (Reporting by Marina Lopes; Additional reporting by Diane Bartz; Editing by Jeffrey Benkoe)