I would then presume that your dial up connection in not active.
Check that you are not in fact activating your network card.
anway You will need to download drivers for your winmodem
follow this link
download an RPM for RED HAT if you want or download the source
When I got mine working I downloaded the source code
unzip and untar with the following command
tar -zxf ltmodem-8.26a9
it will create a directory ltmodem-8.26a9
change into this directory and read the INSTALL file. It will give you instructions on how to install it. (I think there are three commands you have to use)
remember to use the ./mycommand (where mycommand is the filename)in the terminal as just the filename will not look in the current directory
once the drivers are installed correctly issue the command kppp
This is a GUI interface to the ppp daemon, go into options and set up your account there is also a button which allows you to query your modem, if this works your modem is up and going.
If this command does not work go into system tools --> network device control and set it up in there.
good luck !