A device having a keyboard and a display for determining and displaying information relating to the cost of telephone calls. The device contains information as to the identify of exchanges which may be called, as well as information as to the cost parameters of telephone calls placed from a predetermined exchange which is usually the exchange of the user's telephone. The device has an idle state in which a telephone number may be entered and an operating mode may be selected. The device has Timer, Verify and D.E.N. operating modes in each of which telephone cost information may be based on the rates of any of four long distance carriers. In all of these modes the device displays the exchange of the (local or non-local) telephone number entered and information as to one or more cost parameters associated with a call to the telephone number entered. In the Timer mode the device shows the initial and additional period costs and durations and can display the accumulating cost of a call while the call is in progress using any of the four long distance carriers, and including time of day, day of week and holiday discounts. In the Verify mode the called number, day, time and duration of the call are entered and the cost of the call using any of the four long distance carriers is displayed. In the D.E.N. mode the intitial and additional period costs and durations are repetitively displayed for each time period.