For 2 days my phone would not connect to the internet even though my mobile data was activated. The 3g or g logo wasn't even showing. I called orange and samsung and after trying everything they suggested they both ended up suggesting i factory reset my phone. DONT RESET YOUR PHONE!!!! THERE IS NO NEED.
This is what you have to do so you can get back your data network:-
Step 1 - go to settings.
Step 2 - go to wireles and networks.
Step 3 - go to mobile networks
Step 4 - go to acces point names
Step 5 - press the options button (bottom left of the phone)
Step 6 - select reset to default.
Step 7 - should show a list of names choose the one that contains the word internet.
Step 8 - turn off your phone
Step 9 - turn it back on
If you have followed those steps you should have your network connectivity back.
This took me less than 5 minutes to do and has saved me a lot of time, stress and money.
Hope you found this helpful
Enjoy your galaxy s!!!