Upgrade iPhone 3GS

[mraamohamed]

Hello all, I have an iPhone 3GS and it is running 4.1 (8B117) and it is unlocked in America when I was lying there now I am in the UAE and I want to upgrade to 4.3.5 or even 5 when it comes out. I was told that I cannot because of something called firmware or something like that can someone please help me out here I really like my phone but need to update it.

Thanks