A communication system includes, of multiple terminals, a UE with a floor granted that transmits data to an MCPTT server, and a terminal other than the UE that receives the data from the MCPTT server. The UE uses either of a first service performing communication with the MCPTT server in radio connection with a base station, or a second service performing communication with the MCPTT server in radio connection with a relay terminal. The UE, when switching a radio connection destination from the base station to the relay terminal during use of the first service or when switching the radio connection destination from the relay terminal to the base station during use of the second service, buffers the data generated during the switching of the radio connection destination, and after completion of the switching of the radio connection destination, transmits the buffered data to the MCPTT server.