I repeat if you look at the site to get your modem working
www.orpinton.lug.org.uk/modems it will show you how to get your modem working.
I really do mean modem not so called passive devices that need drivers before
some would call modems -others call winmodems- I fear many are miss-sold devices that need Windoze to workthe rest of the missed modem functions and are passive chips devices
require your code and time to add the missing processor/functionality.
In the point over dns mentioned. You can check if it is a dns problem -though you shouldn't need to as the dns is almost always automatic using the dhcp standard protocol -unless you have diabled this. If you connect directly to a site with it's ip address - a number-, but cannot with the site's domain name, you most likely you do not have a dhcp configured, or you have disabled it.
If you want to find a sites number you need to ping from a properly configured machine to the domain name of the site (with a terminal) the reply gives you the ip number. Your own site is locally usually 127.0.0.1 (localhost), or your number/s provided by your ip, try them?
Perhaps' it is a good idea to have a list of a few ip numbers for sites rather than the domain names?