by reading again the thread of how to unlock. it mention there that your phone might have a sim lock. this might be the problem so i search some thread related to this and guess what a found the answer!
now here's how to fix it.
1. after unlocking your phone using msm7227_setool2. check if you have network signal so you won't do the step 2 of this thread.
2. now if there's no signal, open again your msm7227 folder (which is the unlock bootloader tool) and you will see there's another tool which is ms7227_semc.
3. put to debugging mode then connect your usb to your PC.
4. run the ms7227_semc and wait till it done.
5. reboot your phone and you already have network signal again.
i hope that this help you specially for those who are new to this kind of stuff..