Optimal Pricing for Voicemail Services

The uniqueness of phone calls and some other network instruments is precisely that communicating is achieved by the two parties only if the actual connection occurs. The sender pays an appropriate price for the call only if the communication is actually established. The voicemail service in the last decades increases the degree of communication efficiency, by increasing the percentage of successful contacts, by leaving recorded messages without further communication or by encouraging the receiver to call back the original sender. This service should be charged by telecommunication companies. The question is who should pay and how much.