A telephone accessory device for monitoring the cost of a telephone call at the location of the calling telephone. A keyboard is provided through which the number to be called is entered; this number appears on a display and can be checked for accuracy before the number is actually "dialed" by depressing another key on the keyboard. At this time the initial billing rate and initial billing time period appear on digital displays, as well as the billing rate for the next billing time period and the corresponding period duration. Circuitry is provided to continually maintain the billing displays on a current basis, to provide an accurate indication of the cost of the call. At the conclusion of the call the total cost thereof is automatically entered into an accumulator which provides information as to the total month-to-date costs of calls placed from the telephone.Determination of the cost of each call is made by addressing a memory which contains billing rate information, the memory being addressed in accordance with the number of the telephone called.Provision is made to provide warning signals indicating when (i) the cost of a particular call exceeds a preset dollar limit or (ii) the end of a billing rate period is being approached. Information respecting the cost of each call and, if desired, an identification file or account number, may be coupled to an incremental tape recorder to provide a complete permanent record of telephone calls made during a particular time period.Also described is a telephone call routing device for selecting that one of a number of the line circuits which minimizes the cost of a call to a specified telephone number. According to another disclosed feature, the cost metering device of the invention is incorporated in a coin operated telephone to meter payment for long distance calls without operator intervention.