Finally, I have unlocked my iPhone with a pure software approach. Now I can make phone calls, and send out text messages. I can fully experience how good or bad an iPhone is.
I have spent a whole night on unlocking my iPhone. I had my iPhone worked in 1.1.1 as an iPod Touch before unlocking it. So I installed the unlocking software, and wanted to continue using 1.1.1. But then, I found that it had no signal. I read through the unlock tutorial, and found that I must upgrade it to 1.1.2 in order to fix the no signal problem.
I upgraded my iPhone to 1.1.2 for three times. The first time, I forgot to install OktoPrep, so I had to downgrade it again. The second time, jailbreak.jar failed to kick my iPhone out of recovery mode, so I considered that as a failure and downgraded it again. The third time, I used AppTappInstaller.exe to kict my iPhone out of recovery mode, and finally got it done.