how to unlock Iphone 3gs, modem 05.16.05

hello,
have iphone 3gs, ios 5.01,
- have modem 05.16.05.

moved other country can't use at&t anymore, spoke them , offered them money unlocking iphone, unfortunately don't provide kind of service, therefore stuck great iphone can't use sim card...

can please provide me solution?
understood can hack modem i'll ruin gps
suggestion?

thanks!

 

why not sell , buy unlocked iphone?

 

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