Can’t Activate Unlocked iPhone 4 on T-Mobile Using iTunes

Hello Kamilla, in your case, since you don’t have the of official locked SIM card of your iPhone 4, you can pop in other SIM cards (from a friend or relatives) were your iPhone was originally locked to. Alternatively, if you are not sure which mobile phone carrier  the phone is locked to, you can activate your jailbroken iPhone 4 using SAM or Subscriber Artificial Module. Basically, SAM will trick your iPhone as well as your iTunes that your device is running on official or legit activation tickets, even if you hactivated your iPhone. Once you got your iPhone activated, it will stop searching for valid certificates all the times. Aside from activating your iPhone, SAM will also enhance the battery life of your device.

So, in order to activate your iPhone 4 on iOS 4.3.3, all you need is download and install SAM through Cydia. To do that, just simply launch Cydia app on your jailbroken iPhone and then tap on Manage tab followed by a tap on Sources section. Now, tap on Edit button on the top-right followed by tap on Add button on the top-left and enter http://repo.bingner.com as a new Cydia/APT URL and tap on Add Source button. And then tap on Search tab and type SAM in the search field. From the search result, choose SAM and install it, then reboot your iPhone afterwards. Once downloaded and installed, you can check this post for the rest of iPhone activation process using SAM.