Can't connect to mobile internet on iPhone 4s
For American iPhones, go into Settings, then in the first group of settings there should be a Cellular tab. Click this and you will be presented with a list of options to do with Mobile Data and Data Roaming.

If this tab is not present, it may also be called Mobile Data or may be located inside of the Phone tab.

If the tab is not located in any of these places, please contact your mobile phone operator for network specific instructions that may apply.