Can unlock my samsung u520

Question

I accidentally changed my NAM setting from 1 to 2. My phone turned off and when it turned back on it started asking for an unlock code. My code isnt working and neither are the default codes. Is there a reset code or something that will unlock my phone. I have metro and they told me to take it to a store to get it unlocked but i am out of town and the nearest store is to far away. Any help would be great. Thank YouI was just playing around wit my phone and switched it from nam 1 to nam 2 and now it won't let me on it the phone is locked, and my access code is being denied when I try to unlock it. Is there a way to unlock it?

Samsung Sch-u520