Some other location (friends home, work.) and then have someone try from your home.
I am having problems with my dial-up modem. I try to connect to my ISP, the computer comes up "Dialling 086720202.." then comes up "connection failed". I've checked the cord and the plug. All my logon details correct, and I have got the latest driver for it, but it sill won't connect.
I run an Acer Aspire 5520 laptop (model ICW50), with 1GB RAM and 120GB hard drive, running Windows Vista Home Premium. The modem is an inbuilt HDAUDIO Soft Data Fax modem with SmartCP (according to the device manager).
Oh, and the number is correct - in New Zealand, dial-up numbers start with 0867 followed by five digits.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic