[[dN]Eagle]

EDIT:
Correct code!

Code:

public OnPlayerText(playerid, text[])
{
  new string[256];
  new playername[MAX_PLAYER_NAME];
  if(text[0] == '!' && text[1] != 0)
  {
    GetPlayerName( playerid, playername, MAX_PLAYER_NAME );
    format( string, 128, "[Team] %s: %s", playername, text[1] );
    for(new i = 0; i < MAX_PLAYERS; i++ )
    {
      if( IsPlayerConnected(i) && gTeam[playerid] == gTeam[i] )
        SendClientMessage( i, COLOR_TEAMCHAT, string );
    }
    return 0;
  }

  return 1;
}

This is working!