This is a bit embarrassing. But I may not be the only one needed help. If it helps anybody I'm sharing the experience...
When I first got the phone I thought it'd be very easy to peel off the sticker. I started from one corner of the sticker and was very careful to get the edge up a bit while not leaving scratching mark on the phone. But that edged up at the corner was only the top transparent layer (plastic like), the white bottom layer (paper like) was still tightly attached to the phone. I tried from the other corners, Same thing. I tried it several times, couldn't advance any further. I thought it was heavily glued to the phone (but why would they do that). I checked the forum. Oddly, nobody was asking the damn sticker question here.
Well, I got no other choices. So I followed the suggestion of using hair dryer (if there's glue, eraser might make it messy). Patiently waited it to get warm. I then pushed my nail on the sticker edge again. VIOLA, it came off! But there was not glue to the sticker
.
Guess I was just being too careful.
Thanks, guys.