Hope I can help you...
I get my winmodem working at Red Hat 9 & Slack 8.1 without problems... this is what I've made.
The steps are almost the same...
1- first, get the driver: http://linmodems.technion.ac.il/pctel-linux/
2- Unzip the driver...
3- Delete the posible installed modules:
rm -rf /dev/modem
rm -rf /dev/ttyS15
mknod /dev/ttyS15 c 62 79
ln -s /dev/ttyS15 /dev/modem
4- make a symbolic link to the linux directory under /usr/src:
ln -sf linux-x.x.-x linux
5- then I run this command: lspci
this show me the chipset model of all my devices, you have to look at the modem chip... in my case was cm8738.
6- get into the driver directory...
7- run ./configure -with-hal=[modem chip] (in my case it was ./configure -with-hal=cm8738)
8- then run:
insmod -f pctel
insmod -f ptserial
9- and finally run kppp and configure the connection...
Hope it can be helpful...
Any question, just write me out...