How to unlock a found brand new MyTouch4G phone *10ptz*?

i found a brand new tmobile MyTouch fone about 2 months ago. when i found it i was told to break the sim card in order to not get in trouble. and i did. but i cant unlock the fone. i was also told to wait a month after i found the fone so the lost report would cancell after its time. so its been two months and ive tried unlocking it and even with another sim card but it wnt unlock. im guessing my last option is tmobile to unlock it but i dont want to get in trouble or the fone taken away how can i??