Change config variable via a command?

Okay so i am trying to change a config variable via a command.
My problem is when i execute /prefix &2[&5Hi&2] it does not change the config.yml variable prefix.

Command:

Code:java

                } else if(cmd.getName().equalsIgnoreCase("prefix")) {
                    if (sender instanceof Player) {
                        if(sender.hasPermission("cb.prefix")) {
                            if (args.length == 0) {
                                sender.sendMessage("/prefix <prefix>");
                                } else {
                                    StringBuilder sb1 = new StringBuilder();
                                    for (int f = 0; f < args.length; f++){
                                        sb1.append(args[f]).append(" ");
                                    }
                                    String allArgs2 = sb1.toString().trim();
                                    plugin.getConfig().set("prefix", allArgs2);
                                    plugin.saveConfig();
                                    sender.sendMessage("Prefix changed to: "+ ChatColor.translateAlternateColorCodes('&', allArgs2));
                                }
                        }
                    }
                }

Main:

Code:java

    public void onEnable(){
        getCommand("prefix").setExecutor(new BroadcastCommand(this));
            this.getConfig().options().copyDefaults(true);
}
 

Plugin.yml:

Code:java

name: CustomBroadcast
main: net.jc.minecraft.Main
version: 5.11.2014
commands:
  broadcast:
      description: This will allow you to broadcast messages with a custom prefix!
  prefix:
      description: This will allow you to change you're prefix!

Config.yml:

Code:java

prefix: '&5[&bPolarcraft&5]'

 

before getting further help, i suggest adding debug System.out.println()'s and making a seperate executer for prefix rather than using broadcasts' one.