No internet connection after home button replacement

Hi,

After home button and battery replacement (I went through all the guide) my phone works well, but there is no internet connection. To be more accurate, I can make and receive calls, WIFI works properly, GPS too, sound and camera are fine, but... I see "3G" on the status bar, but there is no connection. I'd checked all the settings, and there is no limitations, that could prevent from the apps to use the connection.

What could be the problem?

• I did the same to my wife's phone, and everything working great!