Ticked with AT&T

[outnumbered]

Okay heres the thing I previously had AT&T and I have an HTC Tilt(8925). I just recently switched my service to T-Mobile and need to have my phone unlocked so I can stop using this rinky dink cheap one T-Mobile gave me. Unfortunately for me I switched before getting it unlocked and now AT&T wont give me the code. Any advice or does anyone know a way to unlock it? I'll be purchasing the G! soon but need my Tilt unlocked cause omg I miss getting my emails pronto and my phone has been reduced to an MP3 player for now......OMG the HORROR!!!!! Its a shame I know but it's what I'm stuck with for now....A cheap flip phone.