What do I do to start using dial-up after converting from WebTV to a PC

The MSN TV FAQ says my dad can continue using dial-up. I have completed seting up his modem on his PC. I didn't know what phone number to use so I used the one he used for WebTV. For the username and password I entered the one he had for his MSN account. When the modem dialed out it was able to connect but it gave an error stating that the username and password were invlaid try again. Does he need a new phone number to access dial-up and/or usernaem and password? I tired calling the customer support phone number 800-469-3288 but I was on hold for 1 hr 35 min. yesterday and today at work for over an hour.