I have exactly the same modem ... same problem but under Slackware 10.1.
A friend suggested me to visit: http://www.linmodems.org/
I downloded the scanModem file, ran it and posted the output to email@example.com
I'm waiting for the reply.
I'll tell you the answer...
It's a nuisance !!!
At the moment, I've not found any device driver....