Prior to contacting support, there are a number of additional things that you can check to verify that your modem is working properly.
Check for power to your modem
If you are using an external modem (one not installed inside of your computer), it is possible that the modem is either unplugged or not switched on. Several lights should appear on the front of your external modem if it is currently powered on.
Check that your phone line is plugged into the proper jack on your modem
Modems typically have two jacks — one to go to your wall jack, and one to plug in an extension telephone. These jacks are generally labeled "line" and "phone." Make sure that the cord that goes to the wall is plugged into the modem jack labeled "line."
Check that you have a dial tone
Plug a working extension phone into the jack on your modem labeled "phone" and lift the handset. If you do not hear a dial tone, your problem is likely one of the following:
The jack at the wall is dead
Verify this by plugging the extension phone directly into the wall jack
The phone cord between the wall and the modem is defective
Replace the phone cord with a cord that you know is working and recheck for a dial tone
The cord from the wall is plugged into the wrong jack on the modem
On the modem, switch the jacks that the extension phone and the cord from the wall are plugged into, and recheck for a dial tone.