Important Additional Information In connection with the proposed transaction, T-Mobile US, Inc. (T-Mobile) has filed a
registration statement on Form S-4, which contains a preliminary joint consent solicitation statement of T-Mobile and Sprint Corporation (Sprint), that also constitutes a preliminary prospectus of T-Mobile (the joint consent
solicitation statement/prospectus), and each party will file other documents regarding the proposed transaction with the U.S. Securities and Exchange Commission (the SEC). INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THE JOINT
CONSENT SOLICITATION STATEMENT/PROSPECTUS AND OTHER RELEVANT DOCUMENTS FILED WITH THE SEC WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION. When final, a definitive copy of the joint consent solicitation
statement/prospectus will be sent to T-Mobile and Sprint stockholders. Investors and security holders may obtain these documents free of charge from the SECs website or from T-Mobile or Sprint. The documents filed by T-Mobile may be obtained
free of charge at T-Mobiles website, at www.t-mobile.com, or at the SECs website, at www.sec.gov, or from T-Mobile by requesting them by mail at T-Mobile US, Inc., Investor Relations, 1 Park Avenue, 14th Floor, New York, NY 10016, or by
telephone at 212-358-3210. The documents filed by Sprint may be obtained free of charge at Sprints website, at www.sprint.com, or at the SECs website, at www.sec.gov, or from Sprint by requesting them by mail at Sprint Corporation,
Shareholder Relations, 6200 Sprint Parkway, Mailstop KSOPHF0302-3B679, Overland Park, Kansas 66251, or by telephone at 913-794-1091. Participants in the Solicitation T-Mobile and Sprint and their respective directors and executive officers and other
members of management and employees may be deemed to be participants in the solicitation of consents in respect of the proposed transaction. Information about T-Mobiles directors and executive officers is available in T-Mobiles proxy
statement dated April 26, 2018, for its 2018 Annual Meeting of Stockholders. Information about Sprints directors and executive officers is available in Sprints proxy statement dated June 26, 2018, for its 2018 Annual Meeting of
Stockholders, and in Sprints subsequent Current Report on Form 8-K filed with the SEC on July 2, 2018. Other information regarding the participants in the consent solicitation and a description of their direct and indirect interests, by
security holdings or otherwise, will be contained in the joint consent solicitation statement/prospectus and other relevant materials filed with the SEC regarding the transaction when they become available. Investors should read the joint consent
solicitation statement/prospectus carefully before making any voting or investment decisions. You may obtain free copies of these documents from T-Mobile or Sprint as indicated above. No Offer or Solicitation This communication shall not constitute
an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the
securities laws of any such jurisdiction. No offering of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the U.S. Securities Act of 1933, as amended. Cautionary Statement Regarding Forward-Looking
Statements This communication contains certain forward-looking statements concerning T-Mobile, Sprint and the proposed transaction between T-Mobile and Sprint. All statements other than statements of fact, including information concerning future
results, are forward-looking statements. These forward-looking statements are generally identified by the words anticipate, believe, estimate, expect, intend, may,
could or similar expressions. Such forward-looking statements include, but are not limited to, statements about the benefits of the proposed transaction, including anticipated future financial and operating results, synergies, accretion
and growth rates, T-Mobiles, Sprints and the combined companys plans, objectives, expectations and intentions, and the expected timing of completion of the proposed transaction. There are several factors which could cause actual
plans and results to differ materially from those expressed or implied in forward-looking statements. Such factors include, but are not limited to, the failure to obtain, or delays in obtaining, required regulatory approvals, and the risk that such
approvals may result in the imposition of conditions that could