Ok, here's what happened... I have a T-Mobile branded 8900 i was using my sim with no problems (t-mobile sim) until i decided to see how to unlock it... I did the mepd on the advanced options>sim card and put sixteen zeros now it doesn't accept any of the sim cards i put... i tried At&T several other T-Mobiles but only get "Invalid SIM" I flashed to the latest OS 5 and now when i turn it on it says "this sim card requires an unlock code blah, blah, blah" and it is a T-mobile sim on a t-mobile branded 8900 like i said earlier. Will putting the MEP code fix my situation?