Also check the modem card connector. The phone dials, but will not connect to the remote modem. If you have gotten this far, you have actually made a big leap forward. There are many things which may cause this. First check the signal level on the telephone.
Most phones have a bar graph which indicates signal strength.
The more signal the better off you will be. Try limiting your connection speed to no more than 9600 baud. Pacific Bell only supports 9600 baud. They are working on increasing this to 14,400. If it still fails, try connecting to another remote modem.