Example for GetRadioStationsString()

public OnPlayerCommandText(playerid, cmdtext[])
{
    if(!strcmp(playerid,"/changestation",true))
    {
        if(IsPlayerInAnyVehicle(playerid)) // Check if the player is in a vehicle, so he cannot change it onfoot.
        {
            ShowPlayerDialog(playerid,12349,DIALOG_STYLE_LIST,"Radio Stations",GetRadioStationsString(),"Choose","Close"); // Shows a dialog with all radio stations (including radio off).
            return 1;
        }
        else return SendClientMessage(playerid,COLOR_RED,"Error: You are not in a vehicle.");
    }
    return 0;
}

public OnDialogResponse(playerid, dialogid, response, listitem, inputtext[])
{
    if(dialogid == 12349) // Our radio stations dialog
    {
        if(response)
        {
            SetRadioStation(GetPlayerVehicleID(playerid), listitem); // listitem is equal to the radio IDs, so we should use listitem here and set the radio station of the player's vehicle to that ID.
            if(listitem) // We'll send a seperate message for ID 0 (radio off)
            {
                new string[45 + NAME_SIZE]; // 45 for the default text + NAME_SIZE for the radio station name.
                format(string,sizeof(string),"You have changed your radio station: {FFFF00}%s",GetStationName(listitem));
                SendClientMessage(playerid,COLOR_WHITE,string);
                return 1;
            }
            else return SendClientMessage(playerid, COLOR_WHITE, "You have turned your radio off.");
        }
    }
    return 1;
}