If you have Mobile Broadband tab disabled (or greyed out) in the Network Manager in KDE, install the package modemmanager in your favourite package manager. Or do it manually from a command line as shown below:
sudo apt-get install modemmanager
After rebooting the computer, the mobile broadband tab in KDE NetworkManager should be enabled and mobile broadband connection (3G Modem on Samsung N150) should work alright.
The general settings for mobile internet connection are:
Set your username and password as well as APN, if your mobile phone provider gives you these. Don’t forget to set the PIN, if it’s enabled on the SIM card.
This has been tested on Samsung N150 netbook with 3G Modem in the latest beta version of Kubuntu Maverick 10.10, but it should work in the previous versions as well. Czech Vodafone SIM card has been supplied with the netbook, but not used. Instead, connection using a SIM card of Austrian operator “Bob” was successfully tested.