Unlocking Japanese iPhone 4 (4.2.1)

[sekaijin]

Hello all, long time reader first time poster here.

I have just been sent back to the US from Japan, and only 2 months after having purchased a shiny new iPhone 4 in Japan.

I am now trying to get the phone to work in the US, but I have been unable to figure out what to do and some stores I have visited in NYC have also been unable to provide help.

The J iPhone is also locked to a provider, which means I need to unlock the phone to use it with a US SIM.

Details on my phone are as follows:
iPhone 4
Firmware 4.2.1
Baseband 03.10.01

Can anyone tell me if this phone can be downgraded or otherwise jailbroken/unlocked?

 

[winterny]

Hello all, long time reader first time poster here.

I have just been sent back to the US from Japan, and only 2 months after having purchased a shiny new iPhone 4 in Japan.

I am now trying to get the phone to work in the US, but I have been unable to figure out what to do and some stores I have visited in NYC have also been unable to provide help.

The J iPhone is also locked to a provider, which means I need to unlock the phone to use it with a US SIM.

Details on my phone are as follows:
iPhone 4
Firmware 4.2.1
Baseband 03.10.01

Can anyone tell me if this phone can be downgraded or otherwise jailbroken/unlocked?

Tethered Jailbreak: yes [you will need to have a computer to boot up your iPhone]
Untethered Jailbreak: no
Unlock: no

In the future new hacks may be released that improve things.

 

[oakie]

contact softbank and see if they'll be willing to unlock it for you considering your move back to the US. i had no problems with them doing that for me, but i did it before i left japan when i went in to settle up the contract in full.

 

[labman]

either see if you can get them to unlock it in Japan, or sell it then buy one when you back to the US. less headaches in the long run.

 

[sekaijin]

Unfortunately I did not have Softbank unlock the phone when I cancelled my contract. I asked the person at the counter to do so but was told that was impossible...

I just tried a tethered JB with redsn0w, and an unlock with ultrasn0w. It appears to have worked properly, but I suppose the jury is out until I can get a SIM card from AT&T or T-mobile and test it.

I figure that I may as well post as this may help others in similar situations.

 

[CZK]

Ahhhh the famous japanese 03.10.01 baseband ... You should have said it before!!!!!!