Here is what happened.
I was sleeping. And when i was half awake, i saw my Galaxy S2 has a software update. Being half awake and half asleep me, I thought "Finally Jelly Bean" is out for Samsung Galaxy S2. So i clicked update and continued my sleep. Since i have unifi installed, i am not worry of the data download usage. And since i plugged the charger with my smartphone whole night, i am not worried about the battery as well.
When i woke up, i saw the phone showed Samsung logo. The logo is what we saw when we first turn on our Samsung phone. I thought it was still updating the phone, so i waited for the whole day.
The next day, the logo is still there. I had thought that something was wrong so I tried several things.
1. Restart my phone. I clicked on turn off button for abt 5 seconds then the screen is gone. When i release the button, the screen appear again.
2. Take out the battery. I take out the battery and put it back in. Then tried to turn it on again. It still stucked at Samsung logo.
3. I try to reset it. I push volume up button, turn on/off button and home button for 10 seconds, still nothing happen.
4. I tried what is written on FAQ page of Samsung smarphone web page. Take out the battery, put it back in, do step 3 again but still nothing happen.
In the end, i decided to bring to Samsung service center to fix it.
When i reach there, the person who serve me said they can do it for me. Which mean update to Jelly Bean, but all the data will be gone. I was dumbstrucked for a while. All my picture, songs, message history and phone number will be gone.
Yesterday i got my phone back. All number is gone. The number from when i was in secondary school, college, work and strangers. I need to find all of them back and this is gonna take some time.
Please follow proper step when you are doing software update for your phone.