hello, last week i got a iPhone 3Gs. that was fully functional. it's the first time i handled iphone. in that time I've done 'erase content and settings' under settings menu on iphone. then my phone didn't boot up. i guess i deleted phone's OS also. i connected iphone to my PC, sync with iTunes and restored and updated. i've updated to iOS 4.1. and then when i inserted my SIM, it shows Sim not supported. and showing 'iTunes-data cable' image on iphone. some how I've inserted iPhone supported Foreign Country's SIM and got these menu. but not able to use phone anymore with bangladeshi SIM Version: 4.1 (8B117) Carrier: Carrier lab 8.0 Model: MC147C Serial: 86930R2A3NP Modem firmware: 05.14.02 i am frm Bangladesh can i downgrade this iphone?? if there any step by step guide for me then help me some body help me plz..