1 Press the 10-digit number of the cell phone where you'd like your calls to be forwarded to [source: Vonage 2  ]. Press the pound button (#) or wait for a response indicating that call forwarding has been activated [source: Vonage, ATT 3  ]. Repeat steps 1 through 3 if you're not sure if the process worked [source: ATT ].f you want to stop forwarding your calls, simply dial star-seven-three (*73) from your landline telephone [source: Vonage, ATT ]. There are companies that set up call forwarding from your existing landline or even from a brand new number to your cell phone or other existing phone line.