How to Get Mobile Internet on Unlocked iPhone?
If you have a mobile internet or cellular data plan, but your unlocked iPhone cannot access the web or any data services, you can search online or ask your carrier for the “APN settings.” Under: “Settings / General / Network” screen (image above), you should see “Cellular Data Network.” Enter APN information under “Cellular Data Network” screen. Some carriers might have the iPhone APN entry screen disabled. In that case, you should download an APN edit app from Cydia.