Please help! very complicated issue!

Ok let's start with what's wrong.

I have an iPhone 4 it was bought in some other country(uk/usa).
I used it in south africa(that's where I live) with a gevey sim.

My brother accidently updated it to ios 6 and then pulled it out halfway through the process.

Its now stuck in upgrade mode.

Is ther a way to wipe the iPhone completely clean of ios and everything so I can put my custom 4.3.3 ipsw back on it?

The gevey sim only works with that version(4.3.3)

Thanks