iPhone can I downgrade 3GS?

andybno1

macrumors 68040
Original poster
Nov 6, 2007
3,636
36
Liverpool, UK
ok so basics first:

serial starts 880459
Model is MC637B
baseband is on 06.15.00
iOS is 5.1.1

originally this phone was unlocked (of which I was not aware), this phone was updated to 5.1.1 from 4.3 and still on 06.15.00 baseband.

Can I downgrade the 3GS baseband to unlock it?
 
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