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sbtechie

macrumors newbie
Original poster
Jun 24, 2010
2
0
Hello all,

I am a new member here. I've a very interesting question:

I just bought a used iphone running jailbroken 3.1.2. So, that means I don't have original owner's sim card.

However, I have my own AT&T sim card (without data plan). I would like to upgrade this phone to a normal (not jailbroken) firmware 4.0. I don't care about losing applications or data that came on this used iphone. My questions are:

1) What are the steps to upgrade my iphone to official firmware 4.0 ?
2) Do I need to first restore it to factory settings ? If yes, how can I restore this used jailbroken iphone (running 3.1.2) to unjailbroken factory setting without original owner's sim card ?

3) After restoring, do I need to get data plan (which I don't want to buy) to use it with my sim card ?


Thanks for your help in advance.

Also, I forgot to add:
It is 3GS 16GB.

And I am a newbie, not sure if I've new bootrom or old bootrom. (My Model number starts with MC and 3rd/4th digits are 35). And the serial number is xx939xxxxxx.
 
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