AFAIK, the only open source drivers are speed-locked to 14.4k. If you want the full speed of the modem, you have to shell out $14.95 USD. If you have an HSF chipset, you can also try out the older non-speed-locked drivers
here. Just beware that they didn't work with
kernel 2.6.3-7mdk (Mandrake 10) and I had to shell out for the new ones.
Good luck
Baldrick