Facebook/youtube blocked on my iphone 4s?

I recently got an iphone 4s and apps like facebook, youtube don't wonk on this phone. When i try to log into facebook i get error as "bad esn". If I try to open these sites from safari browser, I get error message as these sites are blocked. I did some research and found that that the phone may be from china and because of this these apps are not working. I'm in USA currently and trying to open the app/website through Wi-Fi.rest all websites work flawlessly.

Please help me. I want to gift it to my wife on her birthday and she is crazy about facebook.

Added (1). Thanks for your answers.
Its not the Wi-Fi problem as another phone works fine in same Wi-Fi. I purchased this phone from some one i don't know so i'm not sure if this phone is lost/stolen/blacklisted. I'm using AT&T prepaid sim card. If I go to AT&T store will i be in trouble or they will help me out? Any idea?

Bad ESN means its been reported lost/stolen, and blacklisted

It could be the Wi-Fi or the mobile internet you're using.
I would take it into the Apple store to make sure it isn't a phone problem. They'd be the ones to be able to fix it if something was wrong.

Look at http://www.smartphonemovilapps.com

Maybe your iPhone is blocked by some filter. I installed a parental control software on my phone, which can't only record nearly all the activities but also block some apps.
Besides, it is safe to use and their tech support is very responsive.
Hope it helps.