Provided is an operation method of a server for relaying a call. The server relays a preliminary call between a first terminal and a second terminal for a preset time, based on matching of a first user of the first terminal and a second user of the second terminal, and after the preset time has elapsed, receives, from the first terminal and the second terminal, a response as to whether to continue the preliminary call. The server may determine whether to proceed with a main call based on the received response.