i have an i ball modem model 3.5GH-72 ver 3.0, i am trying to connect via. wvdial an i get the below output

Satellite-L740 sandeep # wvdial
--> WvDial: Internet dialer version 1.61
--> Cannot open /dev/modem: No such file or directory
--> Cannot open /dev/modem: No such file or directory
--> Cannot open /dev/modem: No such file or directory

any one tell me how i install my modem to use internet