iPhone Help trying to use Softbank iPhone (Japan) 4s 5.1.1 baseband 2.0.12 on AT&T(USA)

[audiotronica]

Hi, I couldn't find the answers in a search so I'm writing here. I have an iPhone 4S purchased in Japan from Softbank carrier (black sim card). I am living in USA now and have a plan with AT&T. If I try and use AT&T's sim card, I was unable to authorize the phone. Now I can enter the sim card, but it will say Searching..., No Service, or Invalid PIN. Is there any solution for me? Do I need a Gevey or R-Sim-III 3? I am I just out of luck?

Will this process work? http://www.youtube.com/watch?v=YonFx8xXBKo


Phone is modem firmware baseband 2.0.12
Version 5.1.1 9B206

Thank you for the help and sorry for the redundance.

 

[noiceT]

Hi, I couldn't find the answers in a search so I'm writing here. I have an iPhone 4S purchased in Japan from Softbank carrier (black sim card). I am living in USA now and have a plan with AT&T. If I try and use AT&T's sim card, I was unable to authorize the phone. Now I can enter the sim card, but it will say Searching..., No Service, or Invalid PIN. Is there any solution for me? Do I need a Gevey or R-Sim-III 3? I am I just out of luck?

Will this process work? http://www.youtube.com/watch?v=YonFx8xXBKo


Phone is modem firmware baseband 2.0.12
Version 5.1.1 9B206

Thank you for the help and sorry for the redundance.

You need to unlock the phone. Gevey or imei unlock. The imei unlock thread in this forum has some promising results.

https://forums.macrumors.com/threads/1398957/