In windows XP/2000, click on start, connect to, show all connections. If you want to change username/password/phone number, double click on the Digital IL icon and change it here.

In windows 95/98/ME, you'll need to goto my computer. Then double click on dialup networking to get to the connection.

If a customer is having connection problems and using windows98 you can try to reinstall dialup networking. Click start -> settings -> control panel -> add/remove programs.
>From here, click on the windows setup tab. *IMPORTANT* MAKE SURE YOU HAVE THE WINDOWS 95/98/ME CD BEFORE PROCEEDING!!!!
Uncheck communications, push ok at the bottom. Now re-open ad/remove programs and click window setup tab again. Re-check communications, insert win98 disc when prmpted. Push OK when done, reboot and try to connect again.

If that did not work, you can try and init string. Modemhelp.org has some good information on init strings. They also have drivers you can have the customer download and update their modem.
You can input an init string in the modems section in control panel. Start -> settings -> control panel -> phone and modem options(or just modems for win98).
In winXP, click on the modems tab up top, select their modem and click properties. You now have 5 tabs. On general, make sure max port speed is set at 57600.
Goto the advanced tab and under "extra initialization commands" input the init string appropriate for the modem.

In win98, select your modem and hit configure. Click on the connection tab. Then click on the advanced button. You will see an extra settings box on this screen. This is where you can put the init string.