1. A method, comprising: establishing, by a server system, a communication connection between caller and a callee based at least in part on a Voice over Internet Protocol connection and via a communication reference embedded in an advertisement that is presented on behalf of the callee; processing identification information received by the server system to determine an attribute of the caller based at least in part on the identification information, the attribute of the caller based at least in part on an identity of the caller or an anonymity of the caller; processing by the server system an indication of a previously stored preference associated with the callee pertaining to charging callers and/or not charging callers; based at least in part on i) the attribute of the caller and ii) the indication of the previously stored preference associated with the callee, determining by the server system whether to initiate an authentication process to authenticate the caller by determining whether a first condition exists or a second condition exists, where: upon determining existence of the first condition based at least in part on i) the attribute of the caller and ii) the indication of the previously stored preference associated with the callee, the server system initiates the authentication process to authenticate the caller; upon determining existence of the second condition based least in part on i) the attribute of the caller and ii) the indication of the previously stored preference associated with the callee, the server system does not charge the caller for a first period of time; billing, by the server system, the callee for the advertisement in response to the communication connection being established via the communication reference; monitoring, by the server system, the communication connection between the caller and the callee to detect a first pre-defined indication provided by the caller; charging, by the server system, the caller, on behalf of the callee, for communications with the callee over the communication connection in response to a detected occurrence of the first pre-defined indication; processing, by the server system, a second pre-defined indication from a user device of the callee during the communication connection, wherein the second pre-defined indication corresponds to a user input made via a user interface of the callee; and stopping, by the server system, the charging of the caller for communication time over the communication connection in response to a detected occurrence of the second pre-defined indication provided by the callee.