I am not sure, but it could be a winmodem. I recently switched to linux as my primary OS and had a problem with my modem. It's PCTel HSP56MR, AMR soft modem (or winmodem, whatever)
After some hassle i got it working as i am connected with it right now, and i'm on linux (mdk 10). I installed slmodem driver which work on a variety of winmodems so it's recommended for a try to anyone that has something similar.
Anyway.. did you solve the problem?
If not.. here's an useful resource: Linmodems.org
- this is where you should start if looking for a winmodem driver for linux. It's the greatest "linmodem" resource.