JOINT FILING AGREEMENT
The undersigned hereby agree that this statement on Schedule 13D dated September 5th, 2008
with respect to the Class A common stock of Virgin Mobile USA, Inc. is, and any amendments hereto
signed by each of the undersigned shall be, filed on behalf of each of us pursuant to and in
accordance with the provisions of Rule 13d-1(k) under the Securities Exchange Act of 1934, as
amended.
Date: September 5th, 2008
| SK Telecom Co., Ltd. | ||||
| /s/ Xxx Xxx Park | ||||
Title: Vice President |
||||
| SK Telecom USA Holdings, Inc. | ||||
| /s/ Xxx Xxx So | ||||
Title: President |
||||
| Helio, Inc. | ||||
| /s/ Won Hee Sull | ||||
| Title: President |
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