One of my friends ask me to make a tutorial on how to connect to the internet from Ubuntu using a dial-up modem. Here’s how to do it :
First go to System->administration ->Netwok, when a dialog appear, click Unlock, enter password.
Click Point-to-Point connection, then fill in the dialog with your dial-up internet account details, as shown.
Click OK to confirm your selection, and you are done.
Click the modem tab, put in your modem device port, typically it should be a serial device or /dev/modem
Hopefully this should be able to help you get on the internet!