How to make calls using your Comcast Digital Voice service Domestic Just dial as you normally would. You can also reference your local telephone book for more information on dialing instructions and calling areas. International To place the call yourself, dial, plus the country code, then the phone number.isit the Digital Voice Center from any computer with Internet access 1. Go to the Digital Voice Center at www.comcast.net/digitalvoicecenter. OR 1. If you are also a Comcast High-Speed Internet customer go to www.comcast.net.