First make sure your xv6600 is connected to your computer via USB and you have launched WModem on the device. On your computer bring up your dial up program (should be dialup networking), click on properties. You should see the XV6600 as your modem and click configure. Mine was set to 230,000 kbs max, so I changed it to the highest number there and I am getting faster connection speeds. This might be the same for you, so give it a try.

Dan