Why does the Device not make certain calls?

During use the device will not make calls for example to International numbers, Check if Fixed Dialling Numbers (FDN) is enabled:
1. Go to the phone menu and top right options menu select settings, select Call Accounts and then “settings” Network provider.
2. Select Fixed Dialling Numbers (FDN)
3. In this screen you can enable/Disable FDN, you may need to know the code. You can also manage the list of FDN from this page.