14 DAY TRIAL // A Support document at Apple.com reveals that, “after upgrading to iOS 3.x or iOS 4 or later you may be unable to use some Cellular Data Network services”. Those include: Cellular Data connection for Internet services, Visual Voicemail, MMS (Multimedia Messaging Service), and Internet tethering. A few troubleshooting steps are offered, including instructions to reconfigure Cellular Data Network settings.
Besides not being able to use the aforementioned services after upgrading their iPhone to iOS 4, Apple claims “You may also see this error message: ‘Could not activate cellular data network: You are not subscribed to a cellular data service’. This can happen if you edited the Cellular Data Network settings—the APN (Access Point Name) details—either manually or with the iPhone Configuration Utility prior to installing iOS 3”, the company explains.
After noting that this particular issue does not affect phone services (which include making and receiving calls or sending and receiving SMS messages), the Mac maker proceeds to list possible resolutions, saying “If you did not edit the Cellular Data Network settings prior to installing iOS 3.x or iOS 4 on your iPhone and you are unable to use Cellular Data Network services, try turning off and then turning on iPhone”. As usual, customers are advised to contact their carrier about the availability and provisioning of these services on their wireless account, in case the issue persists.
“If, on the other hand, you did edit the Cellular Data Network settings, these settings will be reset to the default values after updating to iOS 3.x or iOS 4. You will need to edit the settings again”, Apple reveals, and directs customers to a knowledge base article entitled “iPhone: About Cellular Data Network settings (viewing or editing the APN)”. The document in question explains how to view or edit the Access Point Name (APN) for services on iPhone, which only applies only if the carrier allows these settings to be edited.