An access point name (APN) is the address the phone uses to connect to a mobile network. By default, APNs are set automatically when the phone is first set up. The Access Point Name (APN) is normally retrieved from the SIM card. If you change another operator’s SIM card in the device, the APN settings may be wrong for the operator.
If your phone’s cellular data connection or MMS service settings are not working, those can be set afterwards using the Network Setup application. If you don’t already have, download and install it from the Nokia Collection that appears on the Marketplace.
Network Setup is executed during the next phone startup, according to a SIM card information it configures the cellular data connection and MMS service settings on your phone automatically. Alternatively you can enter settings manually for either or both, to start the application swipe left to the App list, and tap Network Setup.
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Access point name
MMS access point name
Also, some operators may allow business users to access their company network from the mobile data network through a company-specific APN. Such company network access is configured in the device by adding an APN. The operator may also define a username and password for the access point.