I just checked the page on the motorola-site.
I can be wrong, but it seems to me that you can use the driver for 'SM56 Software Modem (Data/Fax) ' to make your modem work. If you follow the installation-instructions on that page you will be able to use your modem to connect to the internet.

You will not be able to use the voice (answering machine)-function in linux, because there seems to be no linux-driver/prog for this function.