If immediately after performing a software update your phone loses the ability to make or receive calls when connected in 3G mode, please first make sure you are in an area with good signal coverage and check with your operator to confirm your voice and data plans are still active. If that is the case, make a backup of your data and factory reset the phone.
If the issue persists after the factory reset, you will need to use the Nokia Software Recovery Tool to recover your phone software:
Step 1. Download and install Nokia Software Recovery Tool to your computer (available for Windows 7, or newer). If possible, make sure that your phone is fully charged.
Step 2. Start Nokia Software Recovery Tool, and connect your phone to your computer with a compatible USB cable. If prompted, select the correct USB mode on your phone: Nokia Suite or Modem.
Note! Using Nokia Software Recovery Tool erases all personal content on your phone. If possible, create a backup of your phone’s content before starting the installation.
Step 3. Follow the instructions shown on the tool. The latest version of your phone software will be installed, and your phone will restored back to the factory settings. This process may take some time depending on your internet connection, and you cannot use your phone during the installation.