External modem

I am having a extremely bad time with my present phone system and dial up. I desperately need a external modem My laptop ia a hp pavilion ze4400. What external modem should I get. Does the external modem work off the wire that runs from the house jack to the port in the back? One wire I had runs from the wall jack to the side of my computer for dial up it quit working. When I dial up with the dial up jack from my house it tells me to call the operator.

The telephone repairmen states it is the modem. The computer tech swears its the phone. Who do you believe? pljames@brmemc.net