How to remove/bypass password on samsung memoir?

ok so i am a cabbie and this guy did not have enough money for his fare. so instead of money he gave me his t-mobile samsung memoir. the problem is when you turn on the phone it asks for a password, which i dont have. i dont have t-mobile but my sister does and i want to give it to her. i tried eight 0s and that did not work. i called t-mobile and they said i would have to open service with them for them to make it usable and i dont want to do that. so what are my options?