A Push To Talk over Cellular (PoC) server for establishing and managing a multimedia PoC communication session for performing a multimedia call service, comprising: a data transceiver for performing transmission and reception of packet data with a session establishment request client and at least one session participation client; a memory for storing information contained in a session participation request message on at least one media type supported by the session establishment request client and media attribute information of the at least one media type; and a processing unit configured to control the data transceiver to receive the session participation request message from the session establishment request client; control the memory to store the media attribute and media type information contained in the received session participation request message; control the data transceiver to transmit the session participation request message to the at least one session participation client; control the data transceiver to receive, from the at least one session participation client, a first response message containing information on one or more media types, of the at least one media type, supported by the at least one session participation client; and establish the multimedia communication session, between the session establishment request client and the PoC server, supporting common media types supported by the session establishment request client and the at least one session participation client by controlling the data transceiver to transmit a response message to the session establishment request client, wherein the common supported media types are determined by the processing unit by comparing the information on one or more media types in the first response message and the information on the at least one media type stored in the memory; and wherein if a response message received in response to the session participation request message is not the first response message, and if the one or more media types contained in the response message is different from the at least one media type supported by the multimedia session established between the session establishment request client and the PoC server and is included in the stored media types, the processing unit is configured to update the multimedia session so that the different media type is supported by the multimedia session. a data transceiver for performing transmission and reception of packet data with a session establishment request client and at least one session participation client; a memory for storing information contained in a session participation request message on at least one media type supported by the session establishment request client and media attribute information of the at least one media type; and a processing unit configured to control the data transceiver to receive the session participation request message from the session establishment request client; control the memory to store the media attribute and media type information contained in the received session participation request message; control the data transceiver to transmit the session participation request message to the at least one session participation client; control the data transceiver to receive, from the at least one session participation client, a first response message containing information on one or more media types, of the at least one media type, supported by the at least one session participation client; and establish the multimedia communication session, between the session establishment request client and the PoC server, supporting common media types supported by the session establishment request client and the at least one session participation client by controlling the data transceiver to transmit a response message to the session establishment request client, wherein the common supported media types are determined by the processing unit by comparing the information on one or more media types in the first response message and the information on the at least one media type stored in the memory; and wherein if a response message received in response to the session participation request message is not the first response message, and if the one or more media types contained in the response message is different from the at least one media type supported by the multimedia session established between the session establishment request client and the PoC server and is included in the stored media types, the processing unit is configured to update the multimedia session so that the different media type is supported by the multimedia session.