I see that your modem is a USB modem. In another thread today I made the statemnent that Winmodems frequently tend to be hard to install under Linux. I also said that External modems that connect to a serial port are rarely Winmodems are are easy to install. I carefully avoided saying anything about external USB modems because I was not sure about them. I got to wondering about external USB modems and after looking on another web page and it said "Many USB external modems are winmodems and should be avoided." The web page also said "Standard serial port (RS-232) external modems are usually fine, no matter what make or model." I hope you did not run out and buy that based on what I said about external modems. I really ment external serial modems. Here is a link to the web page where I found that information:
If it is actually a Winmodem perhaps someone else could tell you how to install it.