Laptop going through modems

I have a Toshiba Satellite 4000 CDS that keeps buring up modems. It first started when it was still under warranty but I could never get them to replace the modem. I bought a Best Data 56K PC Card modem and it worked for about three months and now it quit working also. One day it worked and the next day it would not. Windows sees the modem and when I run the more info on the modem settings it shows all the AT commands.
Any Help would be greatly appriciated. Thank You