This is the Nigerian 419 scam, where they lie to you about winning a prize so you will send them your money and details in order to receive it. In reality, there is no prize, and once they have your money and details they block your calls, empty your bank account and steal your identity. The SMS can have a virus in it so they can program your phone to run up your bill or scam your contact list. If you replied to it, contact your bank right away. Sorry to scare you, but if you act as soon as possible, you might be able to save your account.