I cannot connect to the internet using a mobile data connection on my Lumia (Windows Phone 7)

1. Restart your phone with SIM card inserted and retry your mobile data connection (your phone loads the settings from the SIM card).

2. Enable the mobile data connection on your phone. Go to Settings > mobile network (cellular) and switch Data connection to On.

3. Check that your data roaming is activated when you are not in your home network. Go to Settings > mobile network (cellular) and select Data roaming options.

4. Confirm with your mobile operator that you have an active mobile data subscription (access to internet) on your SIM card.

5. Enable the Wi-Fi networking (Settings > WiFi) if possible, and try searching online to find the Internet APN settings for your mobile operator. To add your settings manually, do the following: 

  1. Download and install Network Setup application from Store (Marketplace).
  2. Start the app, and tap +.
  3. Add the settings manually, select Make this my current APN and tap Save.